Very cool stuff Finn.  Will you be able to use your current exhaust with those rear-sets?  As I recall you made a custom 1.62” header and a hi-flow muffler.  Will you be able to reuse or will you have to fabricate a new exhaust?

And the rear brake linkage rod only needs a minor bend to clear the muffler. Something I haven't done yet in this test fit

To mount the seat on a Cafe can be tricky, there are curves and lines to obey, and then there is the challenge of finding a secure place to mount the sub frame needed.
I could not use the original seat and tank mount, traversing the 2 top frame tubes, because it is destined to be cut away when I get the 20 degrees downdraft carburettor in place. It sits right in the middle of the inlet tract by then.
Luckily it struck me, that the handlebar standoffs that I had left over from the TT handlebar (and which I erroneously had ordered oversize at 28mm) would clamp right on to those tubes and this provide a very sturdy front anchor point for the sub frame.
I like to work with square SS tubing.

The position of the seat is governed by my desire to ride this alluminium tank. I bought it from India, and it was advertised to fit a Honda 400cc. I am not sure about that. It is way too wide up front and generally too wide, it hides the engine too much to my liking.
In short, It has to be cut in 3 lengthwise, with a wedge in the middle discarded, and then welded back together again. This is a challenging job which I will save for when the bike is running.

This detail shows why this tank blends so well in with the lines of the frame, almost as if it was designed for this bike.

Here is just another view of the build.

Cheers, Finn Hammer

Regarding the alignment, this is hard to judge from the pictures, as they are taken from a 1.2 meters distance in a cramped garage with wide angle.

But yes, I have given it a lot of thought. But I am 6'3 and need some space to stretch out without ending out on top of the hump, and with my knees more than halfway past the midline of the tank. The bike is starting to appear mighty nimble after so many heavy parts has been stripped off it. Which is a good thing, really.