You can get h-clips in 15/32". Any good lumberyard should have them.
I would not try to use 7/16" or 1/2". If yor trusses or rafters are 24" on
center, I prefer 5/8" plywood or osb. I use osb for finished garages, but if
it's an unfinished floor (dirt or stone) I would use plywood as osb is...