Difficult
If it was nearer 3mm wall you could take out some of the bend in a regular bow and arrow type bender,
the thinwall stuff will probably collapse?
Dont wanna state the obvious but i will anyway,
take suitable precautions heating or welding on those herras fence panel tubes as being galvanised they'll give off nasty fumes.
Of course you could always cut the corners off and reweld to the correct angles in (horrible toxic zinc fumes and zinc contaminating the weld) or maybe fit pre-made handrail type fitments if you can find suitable ones? The later could give you better take down facility if it matters
My frames need to fit a tarp I already got for free, but I cut up one of the Heras panels, which are damaged scrap ones, and the tube is only 1 mm, so the 90 deg bends bent back out to form the roof angle just by hand, the bottom tube on these panels is made from the exact sliding fit to the frame tube so I've got connecting prices to pop rivet to. All I'm missing is the roof dome peice which I will cut and shut, unless i can find anywhere that can bend 38 mm tube, which no where ive found yet has the dies for. So job done really.
They might be a bit puny for a frame - if the wind gets hold of it...... I have just built a chicken run out of them after a fox had the last lot and a can confirm they are horrible to weld, removing the galvo is almost impossible because of the lack of metal to grind away.
Plus thespace available to insert the unwanted angle at 180 degrees fro the position it was bent at is not sufficient to try and do it in one go so you introduce even more bends , bow andarrow Cut everything into straight lengths , deburr and use a sleeve or insert tube if you can get some to make the angles , drill and bolt or pop rivet the new tube angles in the correct place.
OR
As I'm having to do in a few days , when some foundation concrete & mortar has set .
I'm constructing a four legged arched errection , it will look a bit like a four sided Dutch roof over our pond/water feature and will be covering the roof top with a hard welded 1/4 " Kevlar mesh on the top to deflect crud leaves away from the big oak tree close by. It will also have a black Kevlar soft knitted half inch curtain all round the sides including on two end access doors .
I've made one bend at too much of an acute angle in some 5 mm walled x 1 & 1/4 ally tube ....... That leg responded by being nine inches out of the designed for purpose geometry / square.
I'll be cutting out the bend about 100 mm either side of the witness marks made by the bending jig and turning up a 175 mm long tight fit aluminium bar with champhered ends which will be put in with a hammer and a block of wood after chilling the turned bar in the freezer for a few hours at 21oC to shrink it .
Once in place I'll be using some small dome head 4 mm dia body hammer in in rivets to keep things nice and tight that I'll also be making on the lathe to make a decent straight bit for the uprights & cross bars .
A a new bend will be made in a part of tube free of any insert with at least 100 mm free of any join when it's finally bent in my hydraulic bow and arrow ( cast iron guide inserts not all roller ) bender .
I tried to reverse bend the tube after making a wooden jig to support things , but it turned in the hydraulic bender & put it put in new unwanted angles in a different plane to the original bend. The messed up part now looks more like a corkscrew then a single bend in a pipe.