Hi quatapus.
Unfortunately, not right now. Us devs don't have access to the passthrough mode, but oculus has hinted that they may allow us to use it in the future. Cross fingers.
Use the nose gap, go slowly and be careful. Start with a rough outline. You'll only need to do the setup once, you can adjust later, and it'll get easier to make little adjustments one you have the basic shape set up.
It's also possible to just rest the quest on top of your head (so you aren't looking through it) and walk around to mark all the corners.
I'll put together a "best practices" guide once I finish the update I'm releasing today. Good luck, sorry the first step can be painful.. I'm trying to clean it up as much as I can.