You guys must not have used enough throw for your 3D!
(or too much for your normal rates)

Kyosho Cap232 60-size w/Saito .91 balanced just behind the rear of the recommended range.

Only significant mod:
Stabilized the elevator & rudder pushrods just behind the servo tray to prevent deflection.

It does every 3D move in the book:
Harrier/Elevator
Blenders/Flatspins-upright and inverted
Wall/Parachute
Hover/TR
and excellent knife-edge spins!

Though not really 3D, it'll knife-edge loop, too.

The big deal with any 3D setup are the extreme throws you need - especially on the elevator! Use a linkage that produces "normal rates" at around 18-20% in your dual rate programming (big servo arms). 3D rates are then 100-120%. You should be getting 40-50 degrees deflection.

You should be functionally unable to fly the plane with no expo on 3D rates. You'll need something like -40% to -60% with a Futaba.

If you use a rate that produces snaps at full deflection, you are using slow linkages/servos, have differential or warp in a surface somewhere, or (most likely) are in the "no-man's-land" throw range - too much to fly, not enough for 3D.

Gotta go fly...see ya!