I am getting a hollow center in my sausage. I have an old Toledo grinder that I attach a funnel to front to stuff. I grind pork and deer meat through a 3/8" plate, mixing ingredients after first grind. Grind again, mix by hand again, then clear sinew etc from cutter and plate. grind/stuff on the 3rd pass....all with cutter and 3/8" holes. Hollow center doesn't really bother me as it is about round toothpick size, but I do wonder if it is something to be concerned about. I find that consistency of meat about right with 3 passes. I do have another plate with 3/16 holes, but it becomes really fine grind and usually plugs up anyway. I do not have a 'star' stuffer instead of cutter, and plates can not be found to fit this grinder as it has a flat side on the plates. Comments and opinions welcome.
Some mixers have like a 3 star blade that might help in getting air out. You might want to check out a Cabelas or Gander mountain if there is one close by. I think they sell them separately. I am sure LEM or the sausage maker also carries them. Not sure that would solve the problem but it might be worth a shot.