Verticle rear kick-up?

I'm planning a stretched 28-29 RPU based modified. I'll use an A rear spring on above the axle mounts with the rear spring perch poking through the rear cab panel. I'll hide the 15" vertical kick-up inside the body behind the seat. What's the best way to strengthen the joint? I'm planning on gusseting the 90 degree angle. Any thoughts?

 

1 1/2" x3" 1/8" wall steel rectangular tubing. My other thought was to have a round tube hoop bent up to serve as the upright section.

 

At the area where the kick-up transitions from the frame you could use fishplates. You need to pass the welded seam by, say, 4" on either side.

Here's a sample of mine. The rivet heads are for aesthetics. Eventually I softened the welds around the plate, now it looks more like it's riveted than welded.

 

As a general rule, I always fishplate at least the inside of the splice. However, I've always used a 45 degree kick-up with both pieces mitered to 22.5. With a 90 degree angle, I'm not sure how to go about it. Should I miter both at 45, fishplate it, and call it good? Or is there a better way? The body will be channeled 3". I've even thought of using 2x3 flipped sideways with a cutout of 1 1/2" to slide on both sides of the frame.

 

Cut both pieces at 45deg. For the cleanest look, drill plug weld holes on both sides of the joint and put the fish plate on the inside surface of the tubing. Leave a little extra gap where the fish plate underlies the joint and you have a butt weld with backing in addition to the plug welds. This allows everything to be ground smooth without any loss of strength.

 

me to just came in from Fabing a set of t bucket rails for a buddy of mine , i always run 45 degrees with fish plate on the inside joint.

 

So far, no one thinks I'll run into any strength problems running a 90 degree angle for the rear suspension mounting point? Like I said, I've built and run a couple Model A frames with the normal style kick-up for the rear crossmember. But I don't know how much more I should strengthen the joint over a shallower angle. Thanks for the help!