Help!!!!!!!!!!!
I want to install both 'BG2 Grand Mastery Rules Fix Patch' and 'BG2 & ToB Level 50 Patch & XP Cap Remover', but they have 2 files in common (the 'BG2 & ToB Level 50 Patch & XP Cap Remover' files are bigger than the 'BG2 Grand Mastery Rules Fix Patch').

What do I do???????????

Install the cap remover first. Then the Grand mastery fix.

I understand how to make the alteration. My question is: Does the Grand Mastery Rules fix, allow for the improvement of attacks etc. you get as your characters reach higher levels - especially to level 50 as the 'BG2 & ToB Level 50 Patch & XP Cap Remover' enables you to?

I just went ahead and examined the .2da files affected by the level 50 rules mod you are talking about. No need for you to install the grand mastery fix at all. This mod restores them anyway along with extending thac0 tables and save tables. True to PnP, the only classes that will really benefit from this are non-warriors, since warriors progress to a thac0 of 0 and then stop progressing. If you already installed the grand mastery fix, there is no need to worry and you don't need to uninstall it. The grand mastery fix won't touch the rest of what the level 50 rules patch does.