Hi guys..............I agree with 3dbob, it is not a matter of uneven elevator movement. First thing I did when first notice this tendency was to check differential elev. movement. And yes there was a very small difference that was corrected with no results.
I think that for such a dramatic rolling tendency there should be a measurable differential movement which is not the case....I also checked for deformation in elev/push rod/servo set using a 5 oz weight at max elev deflection. Both halves moved down exactly the same small amount under this load and no deformation, twisting or bending in elev/push rod/servo set was observed.
I think that the problem is elsewhere, and with your opinions and some testing we´ll get the solution.

Thanks

Marcos