2) With the dedenbear boxes, just change it from linkage to base plate, or vice-versa and (up on a stand of course) floor it with the button down and you'll be able to set the rpm. Important note to self: remember to set it back. We've forgotten and it's been a disaster.
3) For us, with a hardtail you want to go on the stop as fast as you can (to let the car settle asap). In our hardtail, we went on the stop at .000. It took a small fraction to come down, but that worked very well for us. FWIW, in our suspended car, we go on at .020.
4) We found shifting on time is much more consistent than on RPM. We shift at 1.00sec so that we're in the low power RPM range which prevents the car from overpowering the stop, and creeping up off the dead stall RPM. It is very consistent.
Hope this helps.