I'm making progress on my conventional layout. Last week I finished wiring up the control panel, and today I started connecting it to the layout. The first thing I wanted to confirm was the boost/buck was working on trestle grades.
I used a 5VCT transformer with a 120/240V primary (Hammond 266M5), and ran the transformer voltage to the center tap of the secondary. Then the trestle inclines are fed through relays. Depending on train direction, the relay will add or subtract 1.25V or 2.5V to the incline block. Running the primary windings in series or parallel from 120V determines which boost/buck level is applied. A Trainmaster with no load maintained almost constant speed with the 1.25V boost/buck. I suspect the 2.5V boost/buck may work better when pulling a bunch of cars.
My block controller determines whether boost or buck is applied, depending on how the engine traverses through the blocks adjacent the incline. Of course, that could also be done with a DPDT toggle switch when the engine direction is reversed.