Thanks for the well written post, it gives us a lot of detail about your issue, which helps us help you.
There are a few options I can think of:
- adjust your gearing and use a free-spinning traction wheel. You might be able to change your gearing some, perhaps raising a middle idler gear, and use a 2.75" traction wheel on the lower holes of the c-channel, lowering them to the same level as the 3.25s.
- try modifying your flex wheels, doing something like this:
3.25” vs 4” wheel traction - #9 by Xenon27
Obviously not exactly like this, as you don’t have 3.25 tractions, but it should get you thinking about similar ways. Maybe 72t gears…