It feels like I have to reach slightly downwards when riding but I believe physics/balance makes it slightly less aggressive than it looks like in the first picture I posted.
I think it rides similar to the angle pictured here but unfortunately I don’t have a picture in motion…
Also a “cockpit” view. If you look closely you can see the “clamping screws” on the 180 degree stem just in front of the nose of the saddle. I touch them slightly when riding and it’s the only minor issue I have with this DIY solution.
Btw if someone wants to tweak this setup with a different handlebar position I suggest getting a 28.6mm seat post and a regular 1 1/8"->25.4mm stem. It would obviously be possible also to use a stem with an adjustable angle for a flexible but a bit heavier setup.
The important part in this setup is the 180 degree bike stem connecting the seat post to any tube of 28.6mm (or smaller with a shim). The rest is just about creativity.