Gws Beaver
I don't have a GWS Beaver, and I have only seen 1 fly. The one I saw fly was a stock plane with no modifications.
The only thing I have heard about is to beef up the wing struts a little.
GWS Planes have a solid reputation if kept within the boundaries of what they were designed to do.
I would be very hesitant about changing the tail surfaces unless someone answers you saying it must be done.
Keep your added weight down to a minimum on these small parkflyer electrics. Weight is your enemy, much more so on a parkflyer than a glowplane.
Keep it light and do your first flight with little to no wind and you should have a blast.
Welcome back to the hobby!