Hopefully this isn’t a complete derail from your thread, we can ask the mods to branch it off if so, but I’m enjoying the conversation nonetheless.
As I’m sure you’re aware, wobbles do largely come directly from rider reaction to uneven terrain. I’ll share a bit of my personal riding experience and commentary, rather than try to tell you things you likely already know.
I guess the only thing I’d recommend trying out is to dewedge your rear to like 28-30 degrees. If you’re using TRAMPA channels I’ve actually got a printed wedge (5-8 degree / wedge & dewedge variants) that has cutouts for spring tensioners and covers the entire baseplate footprint. Was planning on putting these up on Thingiverse eventually but can get on that if you’d like to try them out.
I’ve been riding my LaCroix deck at 36/30 but removed my front wedge and have just been riding a looser damp setup- nothing in the front and reds in the back on 8" pneums/SS hubs.
For Barrett I was running 7" nearly-slicked Innova Inlines & reds front/back. I don’t think I got above 34mph on my test runs downhill but that was due the somewhat gnarly track conditions- at higher PSI I was having to bear down pretty hard on the front trucks to keep my board from popping up too much over the crags.
Geardrive- what gear ratio are you running? I’m curious on your issues with max-speed with the motors not being at the same speed. Obviously there will be some variance there but the larger the gear ratio the less pronounced this is. I’ve run into it on one of my higher KV (220) belt drive Urethane setups but that was at 1:1.8 so the difference in speed was much more pronounced than the 4:1 Kaly drives I ride on more regularly.
Do you ride with bindings? That could also be a factor- I don’t love riding at 30+ with bindings on simply because I can’t shift my stance and tuck in like I can free footed. The cowboy stance I see a lot of people locked into feels okay at lower speeds but I need to tuck if I’m going to sprint at a straight line.
For the record, not trying to argue that channels are the best solution for bombing a straight line. Channels are most stable for me running a slightly drifted line. I just personally haven’t run into any wobbles that weren’t the direct result of my own over-reaction to terrain, and they don’t oscillate in the same manner as I’ve experienced on TKP/RKPs.
Of course YMMV, everyone rides differently and I would never claim anything as an absolute. I just have seen the statement of “channel trucks wobble at 25 or 30+mph” thrown around a few times, and that directly contradicts the personal experience of myself and my friends. I run two MTB builds that both can do 36+ (depending on configuration) on flat even with a heavier rider such as myself. @Skunk recently got some ride time on my Carver with a 4x reds setup & then 0/2 reds setup and had zero issues bringing it up to top speed without even the notion of wobbles.