I just pulled it the other day to try a different clutch fork and I did leave the drive shaft in it and then I set it on a milk crate but in the process I have stripped the threads on one of the motor mounts so it's helicoil time I guess (never done that, it will be a new experience). The problem with just leaving the drive shaft in to pull it all the way out is the emergency brake cable under it. I'd rather not unhook that.
I too have seen some add for a plug. I remember it saying no messy sandwich bags which is where I got that idea. But I can't find that now for anything. I guess I'll call Summit if no one has a clever work around.