Welp, xenologer, now's a good time to educate me, since I've only bought a couple of parts (namely, a differential from Samagaga), but no derailleurs just yet. Below is the frame for my velomobile:



The two beams on the bottom are spaced 5" apart, and are what I'm going to attach the chainline to. Originally, I was going to use Internal Gear Hubs, but the frame weighs nearly 50 KG already, and some people suggested that derailleurs might stand up to the weight better.