foam core layups - advise needed

hey there guys

building a pilot house over a male mold, construction materials are core cell
and h-100 divinycell foam / polyester resin / no vacuum bagging 1.5oz mat / 18 oz 0/90 cloth / 1.5 oz mat

so here are the questions #1 when using flat panels there will be multiple lap joints and some butt joint in the cabin top. (will using a high density filler) in the "LAP" joints provide needed addition stregenth OR is bondo or other low density/strength filler needed just to provide a good fillet for the glass to lay down nicely

#2 the cabin top will be required to support 400 lbs weight the materials are 1 in thick core cell & 3/4 h-100 (total 1 3/4 thick) flat panel (span is 8 x 8.5) so there will be but joints in the material QUESTION will it be necessary to scarf the panels or will a series of off set but joints be ok due to the thickness and fact that two section of flat panel will be layed back to back and it is very thick.

thanks in advance for any tips or insight you may have
mark