Smitty

On the BC the flap width/horn to hinge position can vary, this will give a mechanical speed difference. If you have two channels available that would be better. If not you need to move the horn position. This might also point to problem 2. Are the pushrods the same length?
I always set the TO position with the mid switch position and no sub trim, then you can set each end point.

Hope that helps

Dave Wilshere