Access looks worse than it is. You can get a regular offset ring spanner in there easily to hold the nut whilst tightening with the alien key. I replaced the 5/16” bolts with a M8 x 25. It looks like one of these might be hidden inside the fabrication.
I’ve got grooves all along the pavement outside my property where bolts have gouged. It’s always been ‘a bit awkward’ saying to swmbo would you mind jumping out before I put the car away dear…… ooo

[Linked Image]

Roger
2011 Plus 4