I want a post mount that will tilt back and forth, depending on my position. Upright, it would tilt back a little, stretched out, forward a little. Maybe a spring action to reduce horn pressure automatically.

Is this too far out? Unreasonable? Would there be a market? Would I be the sole customer? Would you buy one too? Is there such a thing?

I don't know that there is such a thing.

CranBrothers makes a seat post with a remote adjuster button you can attach to your handlebar. I think this post only adjusts up/down.

either consider a vastly different frame.. Bernie Mikkelsen has a ride around bike to adjust lengths and angles to design a custom frame by riding an adjustable one 1st.

Or, you might adopt some Brompton parts.. their Saddle adapter pin clamps on top of a plain seatpost.
theirs or something else.. It offers a horizontal tube

then you clamp a saddle clip onto the SAP,or on the seat post ..

Brompton has also made a nice saddleclip, so It allows a vast variety of angles . stepless and mostly aluminum.

WHY would you want something like that? I think I'd find it incredibly annoying. I have a suspension seatpost on our tandem that goes down and back when it engages. If it does it unexpectedly, it really throws me off my pedal stroke. I suspect a seatpost like what you describe would have the same effect.

I doubt that such a thing currently exists. I personally would have no use for one and doubt that there would be a market, but who knows...

So what would be the difference between this and a loose seat? Most riders complain when the tension bolt on the rails isn`t tightened enough and the teat can rock while they`re riding.

I think the closest you could get is a Thudbuster. It's actually a suspension seatpost, but it moves at a diagonal rather than straight up and down.

Another option might be a "noseless" saddle. However, keep in mind that most people use the nose of the saddle to steer the bike, so it will take some getting used to.

The idea came about because when I stretch out a bit, especially when using the aeros, the pressure from the horn becomes really annoying. If I tilt the saddle down to fix that problem, when I sit more upright, the downward tilt is annoying. Figured others must experience the same sort of irritation with a fixed tilt.

I think a spring action mount would work, but as there is no such thing, and I'm no engineer, guess I'll continue to be annoyed.

I had the same problem.

I fixed it by dumping my (almost) universally vaunted Brooks B17 and switching to saddles that were almost dead level from nose to back. The B17 has a pronounced ramp near the rear, especially when being sat on. It's also a bit slippery because of the smooth leather. To compensate, most people set the Brooks up with the nose slightly elevated, like this:



That creates the "hammock" for the sit bones that lots of people like. I don't because of the pressure of the nose when I'm in the drops. I don't like the B17 tilted down where the nose is more level because I slide forward when I'm on the tops.

I solved the problem for myself by switching to saddles that are nearly level from nose to rear. These saddles give me much more of a feeling of my sit bones being perched on top rather than squashed into the saddle. I use a Selle San Marco Rolls for my touring bike:


and Selle Sam Marco Regal saddles for my sportier bikes:


I actually get a level out to set them up level to the ground. I've been much happier with the way they work for me.

There Was a Campagnolo seat post designed by engineers ,
that were not from Mount Tamalpais region.
[& didn't ride off road , more than maybe a Cross Race .. perhaps]
they at the time had a 1 bolt stepless seat post to saddle rail mech,
and learned about .. mountain bikes have a QR seat post
so they thought ... quick release seat post?, and so machined a nice Mountain bike long seatpost with a QR lever on that 1 bolt..


Now, that would be an example of a no tool seat angle adjustment..