The instructions for setting up "Seamless" characters with OCOv2 are confusing, strung across multiple mod pages, and even contradictory (OCOv2 tells you to install body replacers before OCOv2, but Seamless - OCOv2 tells you not to do that with Roberts and implies you shouldn't do it with HGEC). It's such a total disaster that I spent hours the other day finally figuring out repeatable steps for getting it right every time.
In short, this is the order you want to do things in.
- Skeleton (I use Growlf's, but Coronerra's might work too)
- EVE_HGEC_BodyStock and Clothing
- Oblivion Character Overhaul v203
- HGEC texture compatibility addon (from OCOv2)
- Roberts Male Body replacer texture compatibility addon (from OCOv2)
- SR- OCOv2 BAIN (from Seamless OCOv2)
- SE- HGEC CORE (from Seamless - HGEC)
- (OPTIONAL) SE-HGEC BBB all-in-1
- SE- Robert Male v5.2 CORE for OCO (from Seamless - Robert Male)
- If you want an HGEC retexture, this is the place to put it, but test it out in case it doesn't work well with head/body skin tone changes.
- Any animations you want to add (but this is its own swamp of problems)
If you do any gear replacers besides the above and/or after these steps, the neck seams are likely to return. This is sad because I really like Vanilla Gear Redux, but it doesn't work with the above. An exception might be "More Revealing Standard Armors" (which was made for EVE HGEC) but I've never tried it because in my personal, subjective opinion, armor that leaves your belly exposed is just silly (it isn't armor, it's metal lingerie).
Turn off character self-shadowing. Other .ini changes or game video settings are not needed.
Follow the steps above and it should work!
But all that said, there's something that everyone who does this needs to know. The concept of "Seamless" necks is far--extremely far--from perfect. Yes, this will make sure that the 3D models' vertex normals all line up and you don't get any seam from the game's lighting. However no one has ever developed a perfectly seamless transition from neck to body textures. This is true in the Vanilla game with absolutely no mods and it's true after all the mods above, too. In fact, even the Seamless mod itself has very obvious "texture seams" on Orcs (really badly) and Elves (less so on the Wood Elf) right out of the box. These can be fixed (very carefully) with the sliders, but in general, if you start messing with any of the sliders in Face->Tone you can easily and absolutely find yourself with a gross mismatch in color between the head and the body. In other words, if you think the word "Seamless" means, "No matter how I mess with the sliders, the head and body textures will always match," then, unfortunately, you must know this is not true no matter what mods or lack of mods you have.
Also, body texture replacers beyond those specifically in the list above (i.e., HGEC, Roberts) will rarely work well. I've only found one exception (Female Body Retextured by montegris) and even that one is more "fragile" than the basic HGEC texture (i.e., easier to get mismatched colors and less range of color possible).
Some tips to getting the texture colors on head and body to match up correctly:
a) To get this right, it's essential to be able to see what you're doing. When the character generation first starts up, just name the Imperial Male and choose him. Then immediately open your inventory and remove his prisoner's shirt. Close your inventory and then open the console and type showracemenu (and hit <Enter>). Close the console. Now you can create your character while clearly seeing the neck/body connection.
b) Your very first thing should be to go to "Face" and then choose to "Reset." This drastically improves the initial condition of Orcs and Elves. Basically, it puts both the head and body textures in the same place (or very close to it).
c) You will get into the most trouble if you mess with the Face->Tone->Eye sliders. For whatever reason, playing with these really tends to get the head's skin tone way out of sync with the body's skin tone. You can adjust the Face->Tone->Eye sliders, but only within very narrow ranges from the middle.
d) Whenever adjusting any of the tone sliders, don't click/drag the slider and move it wildly left and right. You will get bad results quickly. Always adjust Tone sliders by clicking on the arrows on either side of the slider. You can make small adjustments and see how they are affecting the colors of the head and body together.
e) Use your head a little bit. Look at your character and then look at the names of the different sliders. Depending on the skin tones you're seeing on both head and body, what slider is most likely to help the situation? Although the sliders can get you in trouble, they actually do what they say, so they can also help. Experiment with that (again, click the arrows, don't drag the slider!) and after a while you'll start to get a feel for what you need to do.
f) One of the problems with this system Bethesda created is that you can get weird results sometimes with "in-between" values. So, let's say you recognize that to make your head and body match a little better, you need to click toward "Orange" on the Skin Tone slider that has that option. So you do that, but then the situation actually gets worse, and very confusingly, less orange. That is what I call an "in-between" value, because if you click again (more toward orange), suddenly the next value will do what you want and it will look great. I'm not sure why this happens, but it does. A lot. So sometimes just a few more experimental clicks one way or the other will tell you if you're on the right track or not.
g) This is probably not very intuitive, but the Beard sliders (even with females!!) can be a big help. If you just can't seem to get the colors right with the skin tone sliders alone, try playing with the Beard sliders a little and you can usually get it.
That's about all the advice I think I can give. Hopefully it helps! Happy gaming and modding!