There was a topic along the same lines posted recently, I can't be arsed finding it though.
To answer your question though, there are a couple of garages that may fit a helicopter inside, but it's quite hard to get them in there, and once you've got it in there, you have to get it out, which can cause it quite a bit of damage. It's your call though. I'd recommend you stick with the airstrip garage though - that does a fairly good job.