Originally the other place was going to weld these lengths of angle around the hole to stiffen it up. Would take some time in the shrinker stretcher to get them all to match perfectly. Then would have around 4 metres-13' of welding to fit them. Then grind, planish, sand, planish and run the strip disc over it and check for any distortion once again! Many many hours of work.
Thought I would check to see if the hole was an even distance all the way around like Christos had asked for. Not even close with even one side having over 15mm-9/16" difference from one end to the other!
So took the shortest length and made that the same all the way around marking every couple of inches. Radius corner template a lid from my zip ties.
Cut the long lengths with a 1mm cut off disc and did the corners with my jigsaw.
Pieces that needed to be cutout to make the distance even all the way around.
I got some 13mm-1/2" bar stock and cut down to the depth I wanted to tip the flange. Just used a 1mm cutoff disc and taped where I wanted to stop, 14mm-9/16".
Makes a good way to scribe a bending line to follow later too.
Slide the bar all the way in and bend down bit by bit. Actually found you could hold the same angle down and just knock the bar along and it would bend it down as you went along. Tape gives a good visual to make sure you are all the way in.
Corners are done the same way.
Once a couple of times around I switched to using my flanging pliers to speed things up along the straighter lengths. Bar was still used in the corners and kept at the same level of bend.
Probably took 6-7 times bending a little more getting the 90* bend.
As you see it now only the bar and the flanging pliers have been used.
Was pretty close already but some fine tuning to even any highs or lows. With this dolly behind the flange, I hammered on dolly, stretching the metal, near the bend if I wanted to raise it. Hammered on dolly only at the bottom of the flange if I wanted to lower it some.
One nice and stiff roof panel ready for an insert later on that will be removeable.
The insert can bolt through the newly made flanges with T type rubber seal in between.