Realized I had installed the steel frame gusset on the wrong(aft) side of the frame upright. It is a steel part and was not labelled after powder coating. Turns out that with the bubble doors, the gusset gets a new part number and location (on the forward side). What was the sil trim also has been replaced by a new part that won't fit with the gusset on the wrong side. The plans and joining guide do not make it clear that the parts and process differ with the bubble doors. Had to go to the finishing 1 photo assembly guide to see the correct sequence.
Anyways, I drilled out the rivets and removed the gussets. Moved them forward and drilled new holes on the front side. Removed the gussets. Trimmed the cabin skin as specified in the finishing 1 guide. Made the bends in the new "Sill Trim Doubler" to match the lower door sill outline. clamped in place and drilled. The part which now goes where the gusset vertical used to be was undrilled, so I was able to backdrill into it from the forward frame tube through the holes which had been used for the gusset. I also reused the A5 holes which had been drilled for the horizontal side of the gusset, but these did not line up with the pre-drilled pilot holes, so I have some small holes in the doubler in that area which I will fill with JB.
Finally, disassembled and deburred.
What triggered this was I was following the HBH video when Jon showed the old door sill being installed, and I didn't have that part. That led me to the replacement parts and the discovery of the mis-installed gusset. Guess I should have re-labelled the parts after powder coating, but they are all pretty distinctive from each other and I missed the number change.