My projector will be in a storage room behind the Home Theater. There is a hole between the two rooms. Here's a picture (projector not mounted yet):

Panamorph DCR-J1 and DCR-S1
I'll be putting a framed glass (with 6mm glass) from hometheatreglass.com to keep fan noise out of the HT room.
So, I was thinking of having 8" between the projector lens and the rear wall. Would 6" to 8" between the lens and the rear wall be sufficient room to be able to easily mount the lens without having to move the projector?
Edit: my screen width is 123" and the storage room is 19' from screen, so my throw is 1.9 or so. I shouldn't have to worry about barrel distortion at this distance. I'm more concerned about havingenough space to physically mount the lens into the projector since I really don't want to mess with moving the projector in the future, given how heavy it is.