Rob, I use a crane for my bike by swinging it out to the side. I have a big, strong vertical "bumper bar" on the back of my trailer. It plugs into a standard receiver hitch. On the top end of the bar is a horizontal bar with padding on the end. When I load or unload, the "bumper bar" unplugs from the trailer, turns sideways to put the pad on the ground and plugs back in. The ground contact is outside the CG of the bike when it is swung out on the crane.
Thats what keeps my trailer from flipping over with the weight cantilevered to the side.
Regards, JimL
P.S. I do NOT use tie downs or straps as primary tie down. I use a pair of strong bolt tabs, sticking out the bottom of the bikes. There are a pair of tabs sticking up from the trailer. I use shouldered bolts, ground to a taper, to bolt to the trailer. The bolts have a long taper and I use a bushing and washer to take up the taper as the bolt shoulder size fills into the tab holes. Two is enough and nobody has to deal with salty tie downs, loose strap ends, or the vehicle moving after its loaded. You can stick a pony bar into the tabs as you lower into place, to get the alignment close enough to work with the taper bolts.
The biggest advantage is that this method has completely ended years of crew injuries during loading. The tabs can be any place its easy to access. They do not need to be under the CG. We have a few extra bolts ready, in case we bung one up and have to knock it out by hitting the small thread end. This has been very reliable and sooo easy!