It's a tough call if you should go against your attorney's advice. I'd generally say no, but I personally think he's wrong in this case. Maybe try and explain that you don't have good days. (The law changed recently and attorneys must submit all medical documents now, where as in the past they would pick and choose what supported the case...)

The FCE can take place over a few or even several days if needed. I had to break up mine over several days. It's also a good way for the therapist to document how long it takes you to return to baseline pain levels.

I have RSD as well and my FCE validated how quickly my dominant hand begins the cycle of swelling and pain from any fine motor skills--like typing, writing, grasping paper, etc. My physical therapist used water displacement to measure the swelling that occurred after doing various office tasks. It resulted in my being given a RFC rating with only two potential jobs prior to my hearing. I received a bench decision with the ALJ deciding that my RFC rating was less than Sedentary.