Anyone thought of using fibreglass as a box for their PJ? will there be a problem with the heat from the MH globe?

Im thinking of rebuilding my PJ with a newer LCD and make it as lite as possible.

I've read in the past from those who have used fiberglass that there is a distinct smell when heated. Other than that I haven't heard of any detrimental incidences. I suggest you test a sample first before actually building the box.

Cranky Cowboy build his projector last year using fiberglass for the forward section.
Philw used fiberglass to cover the outside of his wooden enclosure.

I don't know what your parts list is, but I built my enclosure out of Basswood and it turned out pretty lightweight.