I've been thinking about making a board or two for a while now, and have just got round to getting some stuff together.
I managed to get hold of a 24 litre expansion vessel, and today set about a simple test.
So stuck a vac gauge on top and sucked the air out using my kite pump.
I managed to suck out -15 hg or .5 bar.
Is this sufficient for vac bagging purposes? I'd rather not buy a proper vac pump just yet, and the only fridge compressors I've been able to get hold of couldn't pull the skin off a rice pudding, let alone a decent vacuum.
First project will be a landboard, which would be able to take more pressure than a kiteboard with a foam core.

15 in HG COULD be fine, you don't need to push the bag down to make the glass fit tight corners or fine details on boards so you'll be good. for reference if you are using a structural foam (D-cell or corecell) you can suck it to 30 in hg no problem.

IF your pump is really low flow you may have to be thorough ensuring your bag is well sealed to get pressure

You also MIGHT run into issues trying to get the rocker to curve to the rocker table if you are using a stiff core material. As long as it sucks your board to the rocker table you're good to go,

If not using a rocker table but a preshaped core, no concern.