I have a Hollywood rack for two fat tire bikes. I only use one slot but expect to occasionally use both. I'm very happy with the choice. There are some other nice racks out there though.
As for the cargo tray, bungies aren't going to hold a bike in place! You could probably come up with something that would work if have enough extra metal and you can weld, grind, cut, and drill well enough but a Hollywood rack would probably end up being cheaper and probably have a much greater peace of mind level.
TT