First thing to do was to make the solid frames, with doublers front and rear. Made a template again out of some scrap plywood coversheet (like a cross between cardboard and MDF) and marked out the points on the floor to get them right. A bit of cutting and cursing and they were done.
Then epoxy glue them together leaving the doubler that supports the laminated beam to be made once the final positioning is done. Looking from above:
From the side:
Below is a close up, 3 x 25mm solid wood:
Once the solid wood was together I could position them on the solid hardwood base piece and mark out/cut the 9mm ply outside curve. Screwed it in place along the hardwood and started cutting the vertical supports which are 30mm x 45mm. After measuring up on the centreline and marking the position of the laminated beam I could use cardboard to cut the forward top doubler which supports the beam, same as the last frame although this time the doubler is on the front not the back.
Then a simple job to epoxy glue, screw and clamp it all together:
Of course I am lying, it was not simple and I did it in about three different steps. Below is the final result looking from the forward side.
Close up showing the rear of the engine bay and lockers each side:
Looking from aft:
Close up showing the notches for solid wood which will support the cockpit floor.
Finally a morale boosting shot of the frames so far, 1 to 8.