Benny,
On a trailer, some kind of channel or brace to snug the front tire into so you can use nylon straps to pull forward against a solid object AND down. Compressing the front springs won't cause any problems I've run into. Others might differ? I think floor or low mounted solid mounted tie points (eye bolts, whatever) are a necessity. I use four straps, 2 front and 2 rear and haven't had a problem. Fastening the tire itself is a good backup, but I have never done it, although I am a fan of "redundant systems" when hauling loads on the highway.
Loading both bikes forward facing is easier IMO. Then when off loading, loosen one bike at a time, put it in nuetral, straddle bike, while other guy drops the tow vehicle clutch and your on the ground, Repeat for bike #2. (kidding man, kidding

). Check straps when stopping for gas, refreshments or restrooms. Have fun. To me one of the riskiest moments of dropping a bike is loading/offloading on the ramp whatever you use. The leveler the better. More than one person has driven a snowmobile/motorcycle through the rear window of a pickup truck.
And don't take any guff off that Canandinqua crowd for using a trailer.
JH