As you can see, you'll get almost as many opinions about trailers as you will about oil.

Spyders travel well on trailers, but there are some things to consider. As you acknowledged, loading is a question. You will need a ramp that is both long enough and wide enough. The best bet is a tall version of an enclosed trailer...they have the longest ramps and gentlest slopes. If possible, test load the Spyder before you buy. You can get by with shorter ramps, but sometimes have to prop up the ramp, run the front wheels onto boards to raise them as they cross onto the trailer off the ramp, or tilt the trailer to make less of an angle where the trailer meets the ramp. Very few owners have not found an answer, and had to use a hill or loading ramp.
As to width, be sure and measure the clear width of the opening at the rear. Trailers' advertised widths are nominal, and may be from wheel-to-wheel. They also do not take into account wall thickness (on an enclosed trailer), smaller door or ramp openings, or cable counterbalance mechanisms. The RT is 62" wide, and you will need several more inches to maneuver safely. Be sure your trailer can provide this. If the Spyder is to "overlap" the bike, that is if parts of them will sit side-by-side, you will need even more width. The wider the trailer, the shorter it can be (in general). If the machines will be partially side-by-side, be sure there is room for the tie-downs to be angled properly.
Some dealers will let you test load your vehicles before you buy. That is certainly recommended to be absolutely sure. If you do, someone can watch as the Spyder goes up the ramp, to look for nose clearance. The tightest point is as the front wheels come off the armp, and the underbody approaches the part where the ramp meets the floor. If you can't test load at the dealer, once you have a trailer in mind, measure carefully and lay out the dimensions on the garage floor. Masking tape works well for this. You can do the same in the yard, if necessary, using a hose or rope. Test "load" both machines to be sure they will fit. Check to see that the tie-downs will be have sufficient room. Remember when doing this that no part of the Spyder or bike can overhang your dimension marks, even when loading, if you are using an enclosed trailer. Good luck in your search. It takes a pretty long or very wide trailer to accomplish what you are trying to do, but it can be done. Your biggest worry isn't as much about loading the Spyder as it is about finding room for both machines and the tie-downs...and having the trailer balanced for sufficient tongue weight in the bargain.