Congrats! GH2 is a really great camera underwater, using it myself 
As for your question - I don't think you will be able to fit both lenses. Just tried to fit 14-42 II (note it is much smaller than the original 14-42) into 4.33" port (Nauticam 36132) and it barely fits, pretty much pushing against the glass. No way you could use zoom. Is there any reason you want 8mm ? If I might suggest perhaps go with a 6" port (Nauticam 36133) - this way you can fit there two lenses Panasonic 7-14 wide angle and Panasonic 12-35 wide-standard. Both are excellent lenses...since I've got the 12-35 it's my absolute favourite for normal and night dives as it is very versatile. Note that Panasonic might release what can be a potential replacement for this one....12-60 sometime in 2017 but dunno..not much info yet apart from some GH5 shots with it mounted. Same for the next wide angle 8-18...but then that will (and have already!) bring the original prices down 
Good luck!
The reason I want 8mm is that's the lens I own.
While I'm a video hobbyist, I've only recently began experimenting with underwater video using simple GoPro cameras. The thought occurred to me that I could perhaps leverage some gear I already own and improve what I can currently capture underwater. Since I own the GH2 with the 8mm lens, I started searching there first.
It seemed to me that the most minimal entry cost to get me further than I am right now is finding a housing and port for that pair. Anything else would involve purchasing new gear. That may be fine for the future, since this housing/cam/ports seem well supported, but I'm drawing a line at "equipment for existing gear" for this stage.
Knowing that, would you say I'm on a reasonable path or not? Would money spent on a port for the 8mm be a waste? IE: is the performance so terrible that I'm better off with a GoPro and the 8mm port money would be better put towards a better lens and port (6" + 12-35)?
**EDIT: I imagine other lenses and ports would be something I would graduate to eventually. I'm really asking if the 8mm is a viable, entry level lens for the meantime (and a gut check on spending a few hundred bucks on a dome for it).