I have use a vacuum frame that I made myself. My darkroom/dark cupboard is upstairs and so the vacuum part of is provided by a conventional vacuum cleaner that sits in the loft so that the noise doesn't drive me mad and the "exhaust" doesn't stir up dust. My baseboard is 12" X 10" aluminium plate, in which I drilled (very laboriously) holes of about 2,5mm dia. on (I think) a 1cm grid. It works very well, and even when only using postcard size paper there's no need to mask off the unused area to maintain sufficient vacuum.