filler

I'm gonna be doing some filling and smoothing of my stringers. After all unnecessary holes are filled I plan to add a layer of glass to the stringers and floor. With that in mind, can I use regular bondo for minor smoothing or do I need something specifically "Marine"?

I used this stuff called kitty hair it's a bondo resin with fiber glass particles in it, it's light and stronger then anything I've used. If you do go with regular old bondo chances are it will crack in any stress area's. :crossx:

To fill holes in stringers, I use wooden dowls of the appropriate size set in place using West Marines's Epoxy 105 Resin, 205 Hardner and appropriate amount of their 404 Filler ... If the stringer hole are prep'd right and the glass is mixed properly, the dowls will never come out. Also I use the excess of what I mix to fill holes to fill in aby uneven spots.
I wouldn't use Bonbo or anything like it on stringers as stringers typically flex a bit and the epoxy holds tightly where Bondo and such can come free over time.
One thing to remember though, you can put epoxy over pretty much anthing and it will hold but, you cannot put poly anything over epoxy ... you can only epoxy over epoxy. This is basically why I use epoxy glass on most of the repairs I do as I'm never sure of what's been laid down before ... If ever in doubt about what your laying glass on, use something epoxy based.