I was think along the same sort of lines. The over centre catch I am looking at will have a built in lock and I will be able to add a pad lock if needed. I will also be mounting the wheel a little higher so I can put the number plate under it.
I chopped the big ole fixing flange off as it had been welded up by a PO & therefore the hook didn't rotate any more. Cleaned the stub left from the flange up so it slipped inside 50x50 box section & my welding buddy welded it up