jdk81 wrote:
Do the top!!!
Looking at your design, the top is more critical for being plated than the sides.
The issue is where the steel ends halfway through the top of the RHS, any load will cause bending on the top of the RHS. Because the sidewall of the RHS is so thin, there is a chance it will cause fatigue fractures. This is due to the force causing bending, instead of placed in the same plane. ie if the top ran all the way over the RHS, it wouldnt be such an issue. But ending in the middle is a big mistake.
Im not sure I would.
I would pick up the engine mount. on one side
welding across the top could just a spot for the chassis to crack along.
also the forces running through this are upwards only , and suzuki deemed it ok the just weld the factory mounts to only the side face.
as you said idealy you would pickup the other top edge but I belive this will work ok
jmo