I have a Nimbus 26 II for street riding. Recently switched from 150m to 125m.
At the same time I shifted my seat to the far forward position (front higher) because I thought that would make it more prone for me to sit on fat part of saddle when sitting upright.
After a few weeks I find myself riding hunched over. Seems everytime I try sitting upright it pitches my balance too far forward and I have to go back to hunching. I thought it would correct over time, but it did not.
So, I tried something different (which I thought was opposite of what I needed) and put the seat to the far rear (not extreme movements considering the slot in the saddle only allows 1 inch movement at most).
Anyway, rode last night with that arrangement and found I could sit completely upright with no issue of balance. Before it just felt like my waist was thrust too far forward when I tried to sit upright.
Anyway, have attached an image to illustrate - maybe the great Unicycle Physics Gurus can shed some light - or maybe I’m just goofy…
= NOT MY UNICYCLE IN GRAPHICS - JUST SOMETHING I FOUND ONLINE TO USE =
hmm… I haven’t played with the seat angle so much so I’m not an expert opinion…
but it seems like to me that yes, tilting the front up should make your butt sit more to the back of the seat (and thus more on the wider back part as you said). This also changes the center of gravity, but from my experience makes your center move further forward, thus requiring you to lean back more (the opposite of hunching). Of course you could alternately also achieve a further forward center of gravity by leaving your hips where they are and hunching your shoulders forward. I guess the way it feels to me is that you actually ride with a little more forward tilt in the seat/seatpost (kind of like how the unicycle in Photo A looks like it’s tilted forward, not sure if this was intentional), then requiring a little more backward lean at the waist. This then gives your predicted effect of sitting more “upright”.
I don’t run a major upward tilt like you see on some people’s seats, but mine is enough that (with soft squishy Fusion Freeride) I have almost no pressure on the front side of my butt/crotch/whatever. This is of course much more comfortable over a long distance compared to a flat saddle angle where the “boys” are always under pressure. I’ve never actually “looked” from the side via photo or whatever, but I think I sit very upright with the seat with a little more forward lean.
So seems like to me that your method of moving your center of gravity is hunching forward (seems likely you also did this before and now just do it a little more). Instead try leaning the whole unicycle and hips forward but then leaning back at the waist. From the little I now about body dynamics this also seems the better position, as a major problem with biking is that the hips are not rotated far enough forward which leads to shortening and tightening of the hamstrings, so the recommendation for many stretching things is to “open up your hips” and rotate them forward. This of course is hard to do on a wind-aerodynamic bicycle where you need to lean way forward, but on a unicycle seems easy to achieve (I think this pelvis/hips thing plus the use of all the various back muscles as well as stomach muscles is why unicycle riding also gives me far better “body and back therapy” then anything else. If I’m having back pain or tight hamstrings or whatever, a half hour on the unicycle almost always cures it).