You're better off using 3.5-3.7v per cell for calculations, both for a nominal voltage average rps and also to account for voltage sag when motor is running. 4.2v/cell will give you theoretical maximum RPS, which is normally unattainable even on a power supply due to frictional losses unless your motor's KV is out of spec. Yes KV makes it way easier to calculate based on different voltage configurations. I don't know why brush motors aren't advertised in a similar way. You are correct, the pot 'ends' are a fixed resistance that does not change, and the wiper simply touches the track and the appropriate resistance is 'seen' by it. Example a 100k pot, left and right pins will always measure 100k but the wiper being in the middle will measure 50k on either side. Move the wiper to left 25% and you'll see left-mid measure 25k and mid-right measure 75k. (When I first started working with electronics I was surprised to discover this as well, I thought the two 'ends' were isolated) Hence my 'trick' is to use an SPDT switch with resistors matching the total pot resistance to simulate the wiper moving, as the switch in either position will short out one of the resistors. From my Nerf Stryfe build documentation, but the theory is the same as it was used to run two brushless outrunners as dart flywheels. I have not run into problems with the three servo testers I've modified this way, I'm assuming they use the pot as a voltage divider so the resistor values can be flexible (ie 5k you can substitute 4.7k) You can adjust drag brake for that, it's 'softer' than active braking and because it is regenerative it will be better than letting the geartrain bounce off of the spring and waste its energy. Programming card highly recommended Looking forward to seeing progress!