I built my rack for versatility of making it work for several configurationsf. I have since made some modifications that I will explain.
Here's the basic rack I built to hold one spare tire and pack other items in the truck.
I have since dropped the bar going across that the tie downs and tire rack attach to by approx. 3-4 inches. This allowed me to put a bike in the back over the bar and tie it down in the center and also mount my spare to fit under my roll bak lid.
The front and in other places I have used these to put the tie down anywhere I need it. They have never come loose. You can get them for $5-10 at Home Depot or other hardware stores.
One of the things I do with my truck is to be the chase/support truck for my motorcycle friends. Mostly dirt riders on adventure rides but sometimes I have to put a sport bike in. In fact I find them easier than say a KTM 990.
I use a trifold ramp to be able to walk up beside the bike as we load it. I have loaded many a bike by myself and with motor running. As long as you have your footing you shouldn't have any problems.
I like the idea of the rack across the tailgate that was posted earlier.
That could be a very good tie down piece but I find once I tie a bike down with using 4 tie downs in front with 2 going forward and 2 going back that it is pretty stationary and tying the rear down is pretty easy to do to stay put.
The rack can also be used to pack all sorts of things like camp gear and coolers, gas cans, parts boxes etc. The 2 boxes in the back are my tools and compressor that are both quickly removable.
Hope this gives you some ideas.
Mil T