Trimmed the side pcs flush with the corner rib. Put a straight edge across the front and the corners were a bit behind the face ribs for whatever reason. So I ground them down a bit, about a 1/16" in the middle section to bring it in plane with the corners.
Then I placed the sheet on, traced it, cut it and checked it for fit. Tried using clamps and realized it was overkill and then tried some tape. The tape was more than enough to bring them together tightly so that's the method I decided to use. The Loctite worked well. My test pc was strong enough that I had confidence that I could remove the clamps before the 24 cure time. Went well.
I decided since the fit on the corners was so nice that I'd rather use yellow glue and get a hard corner instead of the Loctite which would have given me a softer corner. I want a stable corner in case I need to put some putty in there. With the yellow glue I know it won't move and crack the putty. With the Loctite I'm not sure.
So I applied the Loctite on the front ribs, and the bottom cross members at the lower edge. I applied Titebond II to the cross members at the top and bottom and along the corner rib. Used way more glue than I usually do to make sure I'd get full contact. I also put more glue on the bending poplar along the outer edge that would contact the rib. I wanted squeeze out.
I used squeeze clamps and a backer board on the top section which will have flat stock applied to it and then a crown applied on top of that. I want it as flat as possible so I can just apply the board without screwing around with it.
I used 1 1/2" green tape for the corners. I did a 2" spacing on the 1st round so I could get both sides done quick. Then I filled it in to complete it. This does 2 things. Lets me get both sides done quick. And if there is secondary movement the 2nd round of tape will lock that down. It all worked out well. We'll see if it was successful in a few hours.
Pretty sure I'll be sticking with the single layer of bending Poplar. It came out nice enough where I don't need a 2nd try at it.
And the inside