Re: I joined this site to ask this question...
No matter what you do, even with an open trunk, it will still pressurize, your best answer would probably be a trunk wall, the subs would seal off into the cabin behind the rear seats and minimize pressure buildup in the trunk itself.
Ported or not depends mainly on space/design constrictions, most cars wouldn't be able to fit the ~8 Cubes a pair of ported 15's would need to breathe properly.
97 4runner, 3RZ, 5 Speed
Headunit: Pioneer DEH-P9800BT
Mids: Lanzar 6m
Tweets: Crescendo CCX
Fronts Amp: Alpine PDX4.100
Sub Amp:Hifonics BRZ1.1700D
Substage: 18" SSA ZCON
Electrical: 160 Amp Alt, Duralast Gold, C&D270FR, 2/0 Throughout