Hah! So I also used a Topper rack on my rig to mount solar up, and you did things very similar to the route I went. I didn't use angle iron though, I used some 1" square aluminium tube, long scrap pieces gifted from a friend. U-bolts through to attach to the rack crossbars, then more vertical holes through the tubes to run bolts through the mounting holes on the bottoms of the panels rather than going sideways like you did. I think the angle iron is a better solution but my setup cost me nothing but the hardware. (Even got the Topper rack for free, mwahahaha)
Hah! So I also used a Topper rack on my rig to mount solar up, and you did things very similar to the route I went. I didn't use angle iron though, I used some 1" square aluminium tube, long scrap pieces gifted from a friend. U-bolts through to attach to the rack crossbars, then more vertical holes through the tubes to run bolts through the mounting holes on the bottoms of the panels rather than going sideways like you did.
I think the angle iron is a better solution but my setup cost me nothing but the hardware. (Even got the Topper rack for free, mwahahaha)