[dmjlambert]

Here is a rough hack to your drawing that shows the way I would approach the bracket. Make it out of sheet metal, fairly thin metal straps perhaps 3/8 inch wide, and insert it to grip the metal hole in the cab, then put the grommet on the cab, then insert the dummy neck and attach screw. You may need to use 2 or even 3 of the sheet metal brackets so you get several grip points around the hole for extra stability. This would allow the neck to stick out however much you want, look more stock, and not rely on pressing that lip against the rubber grommet for tension.