They weren't as bad as I thought. I made the internal frames, then checked it fitted the heki, and was square. then I Stixalled the frame to the roof. The frame wood was 45mm wide, in order to ensure I had the required 2mm of stixall in the joint I routed a 2mm deep by 20mm wide channel in the middle of the frame. That way you fill it with stixall push it up to the roof and prop it in place for 24 hours. the side of the frame touch the roof but you have 2mm of stixall in the 20mm channel. I left for a week after coz the stixal in the channel takes a while to cure.
then drill your corner holes up from the inside jamming the hole saw into the corner of the frame but not so much that you cut the frame. then join the dots and jigsaw away, the frame will keep the blade fairly straight but I did cut into the frame a little coz I wasn't paying attention to my line.
If you are talking about the ridges in the roof, that was what it was plastic architrave from Eurocell 95mm x 6mm £11.50 for a 5m length.
Stixall requires about 2mm depth to give it's full strength, if the gap in the joint pushes most of it out then it won't be very strong. You could put spacers between the frame and the roof to maintain the gap.