Please forgive the intrusion, but just wanted to offer some possible confirmation about what you've been discussing and also want to thank you for confirming something I had a question about as well.
I've got a 2002 Suzuki-Lehman trike and am renewing the brake system. In matching brake parts, near as I can tell, Lehman used a Ford 6 3/4" rear differential from a Mustang II (model years 1975-78) This trike is powered by a Suzuki VS800cc engine, but Lehman used a rear brake master cylinder (motorcycle) from a VS1400cc, so I believe you're probably good to go with your 1100cc trike.
On the residual pressure valves, Lehman used only one (not two) and it's probably rated at 10 psi, that goes into the "Y" fitting which is located near the top of the axle tube and then the brake lines from the "Y" fitting run along the top of the axle tubes to connect to the wheel cylinders. This is where I want to thank Y'all. I'd suspected that the residual pressure valve was a valve and not simply a brake line fitting, but wasn't able to confirm that until reading Y'all's thread here just now. Thanx very much and all the BEST with your build ThumbUp