4A director that usually has between 8-12 in class any given year AND has had issues with space to teach (luckily that changed this year). I use to turn my nose up to the bell kits because they really do suck, but they are good at teaching the lay out of the keyboard and getting students started. We just rest them on top of the practice pad. Once you get past that beginning stage, rotate kids between bell kits and the full size keyboards (either by day or throughout the period). If you are going to purchase something, go with the practice marimbas (I like the Adams ones because they have a handle). They are a pain like you said, but ive trained by 6th graders to set them up and put them away in about 2-3 minutes. I believe Majestic has some practice keyboards that also have resonators and wheels (normal keyboards but smaller form and cheaper bars essentially) but I'm sure they cost a ton more than other practice keyboards. You can fit 2 students on each practice marimba if you need to, but if you do octave work you may need to have them trade off on each rep.