RE: trimming a delta?
corkscrew is corrected by aileron differential.
check for this....
fly level flight away from you, pull up 45 deg, do a half roll to the right.
If the plane tracks straight --- no correction required
If the plane pulls off to the right, this means you have too much down aileron travel compaired to up.
You can correct this with most computer radios (try something about 100% up and 80% down travel).
The mix should not affect the elevator component of the controls.
Or...
Use the linkage at the servo wheel/arm to create the differential.\
Assuming servos mounted on top of a wing (pull for up aileron)
You want the neutral servo, with the arm trailed slightly aft toward the aileron (try one spline, or one hole aft on the output wheel first)
This creates control throw with more up than down travel.
If the plane pulls to the left after your 1/2 half roll to the right....
you have too much up aileron travel, and the opposite correction is required.
This is an often over-looked trim aspect.
Bob