We went all through this a couple of years ago.
At least for the 16H 106.5 was the standard. Burlens confirmed this and I subsequently bought a 106.5 from them at Stafford which they had started making again [It wasn't in their catalogue].
As prior to this they weren't available I'd fitted a 106 raised the needle and gone up two sizes on the main to compensate. It ran fine at that except for lumpy running just off and at idle, which could just as well be the worn jet block/slide.
Recently I bought the correct KLG and the engine now is smooth everywhere. Well smooth running anyway... I'd tried loads of different plugs, the only one with the correct heat range being a Bosch, not presently available. Everything else either loaded up or overheated. I still haven't installed the 106.5.....
As an aside Norton habitually used half sizes for the 276, on lots of different engines. No other manufacturer seems to have made a habit of this. As an educated guess I'd say Amal tested the 276 in conjunction with Norton. Their proximity and the time frame of the 16H makes this likely.
I don't have the WM20 card Ian. But there doesn't appear to be any midway adjusters in period photos. But it's not a bad idea to do it the way you suggest to give a bit more adjustment than what is usually afforded.
To my knowledge, the WB30 is the only war time bike that calls for the throttle and air lever midway adjusters in the parts list (with measurements) Mine are fitted as per the instructions.
The only other (WD) midway adjuster that I've encountered is the Clutch cable on the Velo's! That one is supposed to be positioned under the tank which literally means removing the tank to adjust it. I've got mine exposed near the handlebar.:smirk: Ron
I have never seen a .1065 and never seen one fitted to a Norton. My original Amal War years book and later Amal books do not mention a 1065 being fitted to any Norton?
