A couple of points if I may...
a. If you are trailering more than 50 miles or so, do NOT just crank tie-downs tight. Build/get a large block of wood with an upper surface of 8"x12" (or thereabouts) to put under the frame where a center stand would be mounted. You'll want to consider nailing a couple of strips lengthwise to help avoid slip-out. When you crank down your tie-downs your bikes will be resting on the blocks and not subjecting your shocks to various insults.
b. Do NOT put a cover on the bikes. If you do, dust/road grit WILL get under it and between the underside of the cover and your paint/chrome. You will have effectively created a 55mpg sander with your bikes being the grinder's object of affection.
My 2¢.
