Ahh the age old question of:
"To shield or not to shield?"
I would make a point of sacking the top shield on any amiga that came near me years ago! The only point of keeping one would be to hold a 3.5" hard drive in place along with some method of insulating it.
Now I will leave well alone if it does not need to be touched! The only other reason I would remove one is if it is all manky and rusted.
Just recently turned my attentions onto my first A1200 bought back in 1994. The bottom shield had suffered a bit, so armed with some P80 wet-n-dry I managed to clean it up like new. Only did the back part where the ports are. I am quite chuffed how it came out! Will attempt to do the top and see if it will be ok, tbh I see no point but this old machine deserves a bit of love