I can pass on a good tip for a perfect deck/cabin side joint on model Fairey's, passed to me by a skilled pattern making pal,
known throughout his trade as 'cast matching' -
My Swordsman was epoxy/lightweight glass cloth skinned throughout before any Halfraud's paint spraying etc.
Apply a layer of Sellotape or brown parcel tape to the final finished planked deck,
(yes this is heart in the mouth, seat of the pants stuff) and up the hatch surround upstands.
Apply the smallest fillet of P38 car body filler to the bottom edge of the superstructure,
while the fillers still soft sit the superstructure on the deck squashing the filler - hence filling any gaps,
I did mine in 2 hits - one per side.
Sellotape or brown parcel tapes glossy surface should stop the filler sticking to the deck,
if it does stick (mine did) a squirt of Lighter Fluid (Ronsonol in a can) soaking under the tape will release it.
After finish sanding I applied a layer of epoxy/super fine cloth to the cabin wrapping it under/around the P38 fillet
and back up the inside wall of the cabin - just to be sure the P38 stayed in place, should it get knocked.
Hope this is of interest, its scary old modeling but the results are worth the extra effort. regards Paul