reattaching transom boxes

[bibijawa]

I cut out the last foot of the inside of the boat (2 transom boxes and splashwell) when I replaced the transom. Now I'm ready to reattach it. It's all in one piece. Does anyone have suggestions on the best was to glass it in. I was thinking of glassing from the inside(bilge side) with 1708 then filling the gap with thickened epoxy and 1.5oz csm on the outside then fairing . I've read one post where someone glued wood blocks to the inside and then glassed and faired the outside. Ive looked for pictures in the rebuild threads but haven't really seen this detailed.
I have a 1989 20sf.