Kept extending the hole in the top of the port plenum until I have 1/4" clearance minimum throughout. One of my spark plug holes is off center, so back with plastic, prep sand and patch with 2 x UND 90/45 and peel ply.
3 x UND 90/45 over trailing edge corner reshape/repair.
Made the starboard plenum bottom form in the same manner as the port, but from 3mm ply hot glued to a 10mm mdf base at three of the corners, and shimmed on the remaining corner to achieve the twist. A 10mm mdf lip on the edge achieves the rounding I want.
Applied 3 x UND 90/45, plus one straight across between the other plies.
Hot glued some ply to the holes in the lower cowling and molded a pleasing shape with modelling clay. Applied 4 x UND 90/45 overlapping 1" onto cowling inside.