If what you describe as split elevators means one on each side of the fuselage (yeah, what else would it be.. ) then why don't you just control them individually without the torque arm in place?

All you have to do is remove the elevators, even if they are on the plane, just cut off the hinges (most likely CA hinges) then remove the torque arm. Re-hinge it using CA hinges, "mind the gap", as they say in London as you enter the tube trains.. then run separate rods from the elevator servo, which is easy enough to do.

Just join the linkage rods near the servo to go from two to one (see my drawing) then run it that way. You can use the wheel collars as shown, with a set screw, or if you are any good at soldering, wrap it tightly where the two rods join with thin copper single stranded wire then solder it (about an inch long would be fine). Any method woujld work that is secure. No, not epoxy or JB Weld.

CGr.