I can't speak for the specific style of filmholders under discussion. But otherwise, it's not difficult at all to convert regular filmholders to vacuum applications that hold the film just fine. If it's a metal or plastic holder, you turn it into a single-sheet holder, with the backside converted into the vac chamber. Little struts back there are employed to keep the septum from flexing during vac draw. A well thought-out pattern of tiny hole through the septum holds the film; and the back darkslide is cemented or silcone-caulked permanently in place to make the back chamber airtight.

Unless you are simply using a little cordless vac or rubber bulb system, I recommend some kind of bleeder option. The vac pump itself should NOT be piston-style or peristaltic like a diaphragm pump, but be rotary; otherwise pulses in the vac draw can actually jiggle your film plane.