Dave, that spraybar you have to be careful you have it pointed down into the bore if anything. If you set it pointing upward at all it will blow back into the fuel line. The V groove location is covered well enough by the thumbscrew on the throttle plate so that can be adjusted out no problem.

The rotation angle of the mixture tube I figure has a great effect on how well the low and high speed mixtures pan out on it, because this angle has everything to do with how the spray pattern develops.

Looking at the Webra sketch, and my own line of thinking, the top of the V groove should start to form a hood over the groove looking straight down at it to help form a vacuum in the groove as the air passes.

It might be worth the time to rig up a simple flow bench using a piece of clear tube to the carb and then that to a shop vac, and flow water through the carb and try different angles to see what pulls the most water up a loop of tubing.