Personally, I would not want to "attack from underneath." The only way I would consider that would be to remove the mast, place the boat on a rotating jig and have gravity help out in the glassing process. Otherwise you are glassing from underneath, and that is a messy proposition. Much easier to have gravity working with you, rather than against. Just my opinion and YMMV>
As far as the forward bulkhead goes, I didn't have anything separating the v-berth and the forward cavity with access to the nav lights. Instead building a bulkhead, I just glassed in some vertical supports on either side and used T-nuts to screw an access panel in place.
I have been sailing the boat this summer and have put off any further work on the v-berth overhead (and my locker/head cabinet re-configure) until the colder months.
Good luck!