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
