OK, I decided to change the way the tail servos are mounted.

I'm using Mick's rudder servo method, it wasn't easy to get the servo exactly lined up with the hinge line, but after quite a bit of faffing it did work and I have to admit it has resulted in a much more positive linkage than I thought it would.

This freed up enough room to mount the servos on hatches (ie like aileron servos) in the side of the tail.

...Still not 100% scale, but an improvement!