I have some tires that don't inflate very easily on a Stans Flow rim. I was thinking of pumping them up for a while with an inner tube, but the valve does not fit through the hole using any of my existing (presta) tubes.

I don't want to drill the whole, so what are my options?

The valves should fit… I've used normal Presta tubes in mine since I got them. Sorry, that's not a great amount of help to you, but I'm not sure why your tubes won't fit. At the moment I think I'm using cheap Raleigh tubes that came from Merlin.

As a serial tyre swapper I've always used inner tubes with my NoTubes rims…presta should fit fine (don't think schrader would)

Just stuck a random presta tube in one of my flows last night, no probs.

Maybe I need to try again, seems a bit weird. I tested with two inner tubes (might have been the same model though) when I first got the rim, but did'nt think twice as my high roller LUSTS went up with my normal pump. Now I tested 2.4 RQ's and even with a compressor they would not go up.