Which Frame Gravel, wide 650b tires, longer cockpit, more relaxed geo?

[WindChaser8000]

Title is a good summary.

2.1” 650b tires would work, but would prefer up to 2.25” or 2.4”.

Designing for flat alt bar, Koga Denham, so ideally a longer reach, all else equal.

Prefer a more relaxed geometry, with longer chainstays.

So far the closest I have found is the CFR696, but comparing across models and makes can be tricky, due to sizing differences.

Any good options?

[carbonazza]

For such wide tires. Did you consider putting a handlebar, and a road groupset on an MTB frame ?
Most sellers can sell you a matching rigid fork.

[WindChaser8000]

There is a Pro-Mance fork that seems suitable - are they a top tier vendor?

[carbonazza]

There is a Pro-Mance fork that seems suitable - are they a top tier vendor?

I overlooked the bar you want to use... it is a very interesting option for an adventure bike!

Beware that an MTB frame has PostMount brake callipers, while gravel bikes have flat mount.
So maybe go for both PostMount front and rear, because of your flat bar.
Google for "pro-mance chinertown" to get yourself an idea(much better than the forum search)
Personally I would ask Carbonda.
The best being for me to order frame + fork from the same vendor.

[WindChaser8000]

The Shimano road brakes work with mountain levers and vice versa, so I was thinking of 105 flat mounts and XT levers.

I have asked Titan if they make custom bars based on their catalog designs, but haven’t yet got an answer.  They have a couple of interesting bars.

https://www.aliexpress.com/store/group/Titanium-Handlebar-Bar-End/705853_210908902.html?spm=a2g0o.detail.0.0.3fe41b5fxNZ8OD

I may go back to plan A, which was a custom Ti frame, to get a geometry that works with a regular length fork, and not have other potential compromises of adapting the mtb geometry frame.  The mtb frames seem to be built around a 500mm+ fork, which would look strange and would be much flexier and heavier than a sub 400mm fork.  The hta might work with a shorter fork, but that would be more down to luck.

I will reach out to Carbonda regarding a fork.

[carbonazza]

...The Shimano road brakes work with mountain levers and vice versa, so I was thinking of 105 flat mounts and XT levers...

I didn't know that thank you !

What have you done!
I saw this now... https://www.aliexpress.com/item/32850587452.html 

[WindChaser8000]

WRT to interchangeability, I am relying on the web, so be careful.

This was a helpful thread...

https://www.reddit.com/r/bikewrench/comments/9hp871/are_shimano_hydraulic_road_levers_compatible_with/