I have somewhat successfully double dogged a progear 541. I will need to fine tune it a bit and buy some brass to make a spring for it. Currently all i have is a piece of wire wedged between the dog and the housing but it is working. Just very stiff so the handle has about a 1/2 pound or so of resistance before turning.
i will need to grind the plate down another .5 mm or so and shape the dog a bit more so that i can put a brass spring in. it is working right now but I can't screw the bridge down completely.
Can't wait to see it.
Looks good