You will need to know the balance of the UTV's, they are probably rear-weight biased a bit 60% rear, 40% front most likely, or closer to 55/45. You will then have to determine how to load, probably drive the first one in and leave as close to the axles as you can while still having room for UTV2, reverse the second bike in so that most of it is hanging out to the rear of the axles. You should be about right. The best way to figure it out is tow your setup to a scale, unload the bikes and get some axle weights empty, then load the bikes and re-check, you can move them around a few different ways to see how your load is best distributed. I have a snowmobile trailer with a centre single axle, I have to reverse my UTV on it so I have tongue weight, if I drive it on, it has so little tongue weight I can lift it with one finger.