I have customers who've geared down to 19:51 (2.68)
Where one uses the sled the most from 0mph~45mph track speed, (full throttle steep/deep) then can remember lower gearing gives "
track speed staying power"
My observation even with stock,[441 w/43/47] once the sled starts to get geared down towards 20:49 (2.45) when out on the road traveling at trail speeds of 50+mph the rpms may tend to start to lower as you drive with a constant throttle.
The lower one gears, a higher helix angle is being used by the secondary roller; the lower the rpms will be.
Lower the gearing even more and the secondary roller will use a higher again helix angle
or secondary roller will be farther at the end of the "portion" range of
a helix angle.
...so, what does one do to compensate for this?
Look at the primary spring final force.
Say with a 200/320 you start to lose rpms at 55mph and the rpms drift lower to 6700, then raise the final force to allow more spring force to be used at 55~60mph.
Go from a xxx/320 to a xxx/350. Raising that final force by 30 lbs will increase the spring force used at 55~60 mph by about 10~11 lbs and that will increase the rpms by about 300ish.