Most household vacuums run between 50 and 80 inches sealed suction of
water lift (NOT mercury.)  I suspect that much would do a number on
pouches, but if you incorporate a lot of bleed, you probably won't
cause any ill effects.

Of course with the crevice tool held against the bar you won't get a
perfect seal, so the suction the pouches see would be less.  How much
less is a good question.  I've done something similar on our player
many times.  I do it with a piece of tracker bar tubing in the hose end
and the rest of the opening only partly blocked.  The small draft
(draught?) through the piece of hose seems to be "about right."

I don't know about the number of inches of vacuum a tracker bar pump
can produce but my gut feeling is that it's higher since it has a
well-sealed piston moving in a cylinder, but it's not a non-stop thing.
It can only exhaust a fixed amount of air per stroke, and maybe that
alone prevents pouch damage (?)

Joel Hoshaw