Using an .esp as a dependency for another mod/patch?

[chucksteel]

Okay guys, I have been away for some time and I'm very rusty with my modding skills. 

I know in the CK you can't use an .esp as a dependency as it gets stripped away when saving, but back in the day via xEdit (If I remember correctly) I could change the dependency from an .esm version of my mod to an .esp version solving this issue when creating patches.

I have my Beantown Interiors Optimization patch which relies on my Beantown interiors .esp, I used an .esm version of my mod to create a new patch  but I'm stuck using the .esm master. I'm trying to update both but have been running into a brick wall and now xEdit doesn't seem to let me edit the extension of masters. 

I've messed around a bit, I've tried to add masters, clean masters but I can't remember how I had done this in the past. 

any help would be appreciated, 

chuck