I want to do intracelluar and extracellular staining on differentiating myotubes, but I know they would be too large to run through whole. I've seen a few papers saying they've run myotubes through a flow cytometer though.
It is possible to do flow cytometry of myotubes until unless you make sure that there are no clumps. You need to adjust the forward scatter to see the cell populations. And it is better to have low cell density in the samples. See the following paper for more details.
See if you can get access to a Biosorter from Union Biometrica. It is a large particle sorter but also does accurate analysis on object length which you will not get on a conventional cytometer.