Changing GP Big Stik 60 to a taildragger?
First, remedy the nose heavy situation. Then you will only have to move the mains just ahead of CG. Don't forget to re-enforce. if you move the gear.
You could also mount the rudder(tailwheel) and elevator servos into the rear fuse, helping with the CG (and tailwheel linkage too).
Mine is still a trike, so this is just my $0.02 worth...