RE: Excelleron 90
Ken, my ST needed to be 1/4 turn leaner than stock after break-in (also using a Cline regulator as tank is on CG)
Some mods..
Built as a pattern only (no 3d)
Using MK ball bearing links stand offs were too short with the deep bevel on the surfaces. Mfgd my own from some delrin stock and installed ball bearings (min 3:1 mechanical advantage)
Home made CF cannister (3.5 oz).
Removed counterbalances from rudder and elevators and spliced them on the h.stab and v.stab
Dual elevator servos.
Pull pull rudder above stab and new mount for servo
Tank to CG
HS55 throttle servo in the engine compartment with ball links at both ends.
Bolly gear 2.5 inch wheels
I don't have any way to compare the performance of the modded surfaces to stock (with counterbalances) but the plane is locked in stable in all vectors. Using somewhat lower throws (Elev 14 degrees - Ailerons @ 12 degrees with 7% differential - Rudder 35 degrees). No mixing anywhere (except the obligatory throttle bump for full rudder stall turns)
Good Flying
mike