More reserve vacuum is always better. I've added an extra vacuum tank to some applications, such as trucks with a vacuum shift 2 speed rear axle, by recycling a disposable 15 pound Freon canister, bracketed under the bed or inside a frame rail. An inline check valve between the engine and the reservoir will prevent vacuum loss in case of an engine stall. Then plumb the accessories such as brake booster, wipers, etc. to the reserve tank(s).
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!