I had to install a proportional valve on my Liberty sidecar. Rear and sidecar brakes are linked with a valve in between. It allowed me to adjust the sidecar brake to allow for straight line stopping. Without it the sidecar brake sent me to the right. I bought it from JEGS.
To clarify the rear and sidecar brake still send me slightly right and the front brake sends me slightly left.... before the proportional valve the sidecar brake sent me severely right and just the right combination had to be applied to go straight. Before the proportioning valve most of my hard stops were in a zig zag pattern.
Regarding the electric lean / camber control:
I absolutely love mine. I was very hesitant to pay the extra $$$ for it, but I was already in so deep that I just went for it. Now I'm VERY happy that I did so.
I just did a 900 mile road trip and I'll tell you that I used that thing a lot on my trip. I can adjust based on weight in the sidecar, but I found that I also adjust quite a bit as the road lean changes. I was quite surprised to find that some roads lean right, others left, others are just humped in the middle.
Lastly, the speed of travel has an effect on the lean as well. Some of the freeways on my trip were 70MPH and folks were doing between 80 and 85. When I got up around 80 I noticed that I needed a little more lean out, not because of the road or weight, but due to the aerodynamic drag on the hack. No problem with the electric lean.
It takes a bit to get dialed in, but once you do, you'll be addicted to it.
As for the proportional valve ... sounds interesting, but I have not tried one. My rear brake also pulls me right, but I LIKE that. The front pulls left. Use both and I stop straight. Need to go left a little, I use the front brake more. Need to go a bit right, I use the rear brake (assuming I'm not able to just accel to go right).
Anyway ... those are my thoughts. Best of luck.
Proportioning valve: I ride a '83 Yamaha Venture Royale The MkI's and II's all had a proportioniong valve for the front and rear brake. Apply brake pressure with the foot paddle and you would wind up with a 70/30 split on brake power front/back. don't see why you would not be able to set it up for the handbrake. How to hook your sidecar in I do not know. Suggest you visit venturerider.org and ask about retrofitting your bike. Great group of people. there's even a number who run a hack and may be able to help you with hooking the car in as well
