I'd take a dremel tool or die grinder to the one MAP sells for the Atlas and do a port match to the carburetor throat.
I made a twin carb setup for Mikuni 34mm carburetors out of what was available for the Commando back in the early 90's. I couldn't find anything for the Atlas at the time. I hand filed the flanges at the carb mount end down until they were round. Then used a small round file to make a little indented ring all the way around, like the indented ring on the Mikuni intake end. I used automobile fuel filler hose for the rest of the manifold. The carburetors are horizontal. It's a bit tough on the throttle cables, but it does work very well. No hiccups and peppy with 3-inch velocity stacks on the carburetors. The fuel filler hose makes it easy to change the length of the intake. My filler hose sections are at the minimal length. If they were any shorter, the mounting flange on the fuel bowls of the carburetors would touch, and probably rattle a bit from vibration.
Any chance you can push the 36mm Mikuni into a 34mm rubber adapter? I just measured a 34mm adapter I have and the opening at the manifold side is 36mm. It's 40mm at the carb side. If you could shove a 36mm Mikuni into the 34mm adapter it would work flow wise. You could have the adapter I have, but it might not bolt on your intake. It came with the Norton Mikuni twin carb conversion setup I modified 30 years ago.
I've had a set of Mikuni bendy throttle cable gizmos similar to that for 30 years in my pile of stuff drawer. I've tried a couple of times, but I can't get my cable ends to go through them without some serious modification to the ends that I haven't felt like tackling. I should try doing it again after I get a set a spare cables in case I really mess it up. Maybe I can get those that you used to work. Treatland has a lot of great stuff. Thanks
BTW my carburetors are horizontal not slanted forward. If mine were at the same angle as they would be on a Commando motor, they would work without need for the bendy part.
Schwany, I didn't use the jam nut for final fitment.
After putting the jam nut all the way on, shortened the adjuster to about only a quarter inch of threads.
After cleaning up the end, when I removed the nut to do a final clean up of the threads.
This gives it room for the fitting to slide around the bend.
I didn't have to do any modifying of the cable fitting.