Plastic Support Insulation on open Ceiling

If I stapled some plastic to my ceiling rafters (24in o.c.) would that be enough to support R-30 insulation if layed between them? Drywall won't be installed for some time. What is the minimum thickness platic recommended?

Thanks

insulation

Why aren't you using paper backed insulation stapled to the joists? If you use the proper unfaced insulation it is wide enough so that it has to be pushed into the spaces which usually holds it up, so your plastic would just have to keep it there, not support it.