You can (and should) cut the tops of the thighs down, Chris. They can pretty much be trimmed down as needed for a correct fit. I always suggest removing all return edges in the following areas as seen in the screen used armor below. BUT... do a test fit first BEFORE gluing anything together. If not, the pieces will be loose afterward and may not fit correctly. There is a term we call "armor bite", which means that the return edges rub, chafe or pinch you while suited up. Better to to be proactive than reactive to prevent this.
I hope you are thinking about aiming for Centurion, and removing materials in these areas will not affect approval at any level.
Thigh tops- Return edge has been completely removed. Note that there is also none in the "groin" area, which can (and will) lead to chafing. When cutting these down, just follow the same lines /shape of the existing top.
Elbow openings- Since you will spend a lot of time holding your E-11, your arms will be bent in. Losing the return edge here will stop any discomfort.
Biceps- No one sees the tops anyway, so why not be more comfortable!
Shoulder bells- Having a return edge on the bottoms adds to a "thicker" look, but this can also cause them to ride out and leave a large gap between the bells and chest/back plates. (Not a desired effect). You can trim most (or all) of it off if needed.
Wrist openings- You should trim this off 100%, (especially in the "hump" area I highlighted).
Keep asking as many questions as you like, sir. We are here to help!