Is it 2" too long when you're standing up? If so, don't change it at all, because that will be just about right when you're seated.

Even if it's too long when you're seated, I'd hesitate to change anything about a fire rated suit, since it's probably stitched with fire resistant thread, and anyone who alters it for you probably won't have that kind of thread.

Unless the extra 2" is somehow really uncomfortable, or otherwise a problem, I'd say leave the length alone.

 

I actually had it done already, they only shortened the outer "boot cut" portion of the pants leg. The inner "cuff" that seals against the leg wasn't touched. The guys at the shop said it's fine to use cotton thread, which is what was used. They also mentioned that if you sew on any patches to only use very little cotton thread, so if in a fire the patch will "burn off" instead of catching fire and creating a hot spot against the suit.