Trailing arms

[pigeondave]

I have noticed that my trailing arms on the rear are slightly banana shaped. This has caused the rake to drop a little.

Two questions for the forum.

Is there a preferred supplier of steel both the rectangular section, the suspension pick-up and the short length of cylindrical tube as well as the rubber bushes?

Should I rose joint one end so that I can get half turn adjustment on the rose joint. I remember years ago that this should only be done at one end.

Also is there any advantage to making them J shaped? I think this was done so that could run slightly longer dampers.

I tried using the search function but not coming up with a lot.
Dave