I'd run a 4" pipe about 18" long. No need for any kind of bleeder valve- - - - -the vacuum will go away on its own within a few minutes of engine shutdown, and there's no problem with keeping some vacuum in reserve all the time. If you want to deplete the reservoir for some reason (can't imagine why) just pump the brakes a few times with the engine off.
Jerry
I realize the engine can only generate so much vacuum, but will the vac in the canister continue to increase as the engine is running, and I'm not using it? I guess it should work... it's how boosters themselves work. I'm just curious, I guess.