Roof Penetrations in flat roof for lineset/whip
I am putting two 2-ton heat pump units on a new construction flat roof. The lineset will be 3/4" suction and 3/8" liquid and the whip will be 8 gauge. The roofers are coming soon and requested that I put the penetrations in. I have not decided on a HVAC installer but want to make sure that I leave a viable penetration for whomever I do hire.
My plan was to place a 3" rubber flashing boot and a 3" PVC vertical pipe with a 180-degree elbow (similar to my vent stack penetrations) to keep water out for each unit. My questions are these.
1. Can the lineset and whip be run through a single PVC and then sealed post-HVAC installation with spray foam? Or do I need a separate penetration for each?
2. Should I put in metal flashing vs a rubber version?
Thanks in advance!