I prefer to use a 5# deadblow hammer. I’ve also used an axle but it does leverage the weld a little more from what I’ve seen. When you have to move the strut more than an inch you can expect the paint to crack but I’ve moved some almost 2″ without issue.
I use a combination of deadblow hammer, crescent wrench ( attitude adjuster)
Another real mechanic’s hammer ( Snap-On or MAC ) rubber coated to support and counter weigh the impact from the other hammer ( this is the only way that works for me to avoid cracks at the welds ( you have to support from the opposite side you’re hitting at )
Last one I did I used a piece of unistrut channel. It fit over the strut/brace and allow a lot of leverage and control. Big Crescent wrench for tab adjustment.
I feel like I am horrible at seat mounting, but the unistrut felt right.
I have to move the right strut by cutting it off and re-welding on every kart I’ve owned. You have to pay close attention to engine clearance. For bending the left one, I use a pipe with U bolts and move it around to get a wide bend. You have to careful where you’re bending it not to kink it and check the welds after.