OK done with the tail. Thanks for your suggestions, guys. In the end I went with my original idea, replace the bit of balsa that got torn out, and from behind I stuck on an appropriately sized piece of 2mm birch ply.
I thought about choosing a different hole but the thought of waiting for control horns put me off.
Hopefully you can't really tell there was damage.
The new servos cut the slop in half. Used to be pretty wiggly, now it just moves about 1mm on the LE of the elevator counterweight, maybe 2mm on the TE of the elevator. Centering seems OK but that's not under load.
The replacement servos (TGY-S306Gs) are also really fast... not sure what difference that will make. Nice thing is they come with a servo arm that is 19mm long from spline to hole, so you can get full throws and then some.
The TGY-210DMHs I previously had and chose after testing had very good torque and if only they had less slop I would have been extremely happy with them. I guess this is lesson learnt to not use sloppy servos? We will have to see this weekend, hopefully I can get the aileron servos done up in time for a fly.