Ik heb zelf geen ervaring met de vergroter en de pomp, maar misschien is onderstaande 'gebruikerservaring' interessant (komt van hier):

My experiences with an vacuum easel are not very successful. I have an
Durst G139 enlarger and had the chance to buy an original vacuum easel
(GRAVACU) for it. This thing has a size of about 90x70cm and has several
concentric grooves for different sizes of film/paper. You can put special
(and unavailable) hollow pins in it to adjust air flow fron center to the
outer grooves.

I got the original vacuum pump from durst for it. First tests were
absolutely unsuccesful. The pump run, the vaccuum meter built in the
easel showed minimal vacuum (the needle just moved a little). A whistling
sound was heard, air was sucked into the groves. A very flat PE paper
didn't show _any_ suction whatsoever, it was obvious that only the inner
grooves must allowed to suck, the outer (open) groves (max grove size is
60x70cm) must be closed.

A few weeks later I found brass tubes with the exact diameter needed for
the hollow pins. A disassembly of the easel showed how these pins are
supposed to work, a little work with a Dremel tool created a few. Now I
could cut off the outer grooves and use only the inner ones. The next test
showed a little more whistle, the needle of the vacuum meter moved some mm
and there was just a little suction felt, the flat PE paper gave some
resistance to movement. However,it had to be exactly concentric to the
groves and had to be very flat... a little movement or usage of non-PE
paper was impossible.

So I tried to use a household vacuum cleaner (noise and less measured
vacuum) and finally bought a much larger pump (from a collator) and tried
this. The result was disappointing: much noise, whistling, a vacuum meter
that showed a pressure of 10% normal pressure etc. just to hold flat PE
paper concentric to the easel. Any trials with (not very flat) baryta
paper or eccentric positioning failed, as soon as air got under the rim of
the paper the suction was off.

After several month of tinkering, testing, getting supplies and buying
expensive machinery I gave up, bought some flat MDF boards as easels and
a can of 3M non-permanent spray mount and forgot about the thing. Maybe
it's possible to use a vacuum easel successfully, but I couldn't manage.
At least the GRAVACU is specifially made for certain sizes of paper/film
(I suspect it was usually used with flat repro film) and doesn't work with
actual photo paper sizes. There were two versions of the GRAVACU available
(for metric and inch sizes) and this alone shows that one easel isn't
useable with even slight size differences... the metric sizes were
sometimes just a few mm different to the inch sizes of repro film.

My hopes of getting stubborn baryta paper to lay absolutely flat on a
vacuum easel were crushed. However, a 19mm MDF board with blue 3M spray
did this nicely... anyone interested in a strong vacuum pump? I will keep
the easel, it's strong, flat and black.