SWMBO's got some stuff stored in a few of them and the pressure
*seems*
to hold just with the valve closure.

Yes but does SWMBO use the amount of pressure required to crush veneer
flat onto a substrate?

OK yes of course she does, and when she packs clothes in a suitcase she
achieves a density only slightly short of neutron star level. But
whether the bag holds at the at level for long enough to glue to dry I
don't know.

Someone must have tried using a space bag, but I couldn't find an
example when I googled.

As far as cost goes though, you could buy a $600 commercial veneer bag
set up, make the dining table top and still save a bundle over what the
solid mahoghany top would cost you... Even more so if you flogged the
equipment on ebay afterwards.

Ebay creates an interesting new tool dynamic. The cost of tool rental
for a day is exhorbitant, sometimes a quarter of the cost of a tool,
but if you only need it once it is cheaper. Ebay means that you can
justify the cost of the tool with SWMBO as being cheaper than renting
since you could in theory sell it again on Ebay, or at least you can in
theory in practice SWMBO will point out eventually that you never do
sell the tool afterwards and moreover one does not have a degree in
rocket science from MIT to work that out.