Not sure if you guys have checked out another option yet, but a company called Pit Bull makes awesome trailer restraints.
I'm not affiliated with them in any way, but would strongly recommend you check their products here:
http://www.pit-bull.com/category/trailer_restraints.html
I've been using them in my last 2 trailer and when the bikes are loaded they are rock solid. One of the best things about the product is that when the bike is in the TRS the suspension is free to move - so you're not loading the forks/shocks and compressing your suspension in any way. While I'd previously used Baxley chocks (and have a condor for my wife's pit scooter) you have to compress the suspension to ensure the bike won't move around, which has it's own downsides as a result. Another benefit of the TRS is you can disconnect the latches and set them aside, just leaving the plate mounted to the floor and they're <almost> flush with the garage flooring. The only thing really sticking up are the buttons that the latches grab. While I don't remember their height it's minimal (less than 1/4") and if you use your garage as another room once at your destination with carpeting down (or not) the buttons aren't really noticeable. I mean they are there - but it's not a big deal. Also - you can lay out multiple TRS plates in your garage for different configurations - taking two bikes this trip, but might need 4 at another time? No worries - you can create a 'staggered setup' with bikes facing front/rear and offset from each other, providing ways to easily (and securely) get more bikes in the same amount of space without killing yourself.
Best story I've heard about Pit Bull (and later, saw pictures) of someone using a TRS system trailering their bikes to a racetrack and they flipped the trailer over on it's side (smallish box trailer, late night coming back from track - additional details unstated). When they opened the doors the bikes were still completely attached and sitting on the 'floor' just as if the trailer was upright. The rest of the contents of the trailer were all over the place just as you'd imagine.
I also have to say that the company is top notch to deal with - which goes a long way in my book. I have slightly different axles on my Triumph track bike (due to running aftermarket axle adjusters) and the standard pins wouldn't fit. Called their customer service and they asked me to confirm what I was using, take some pictures and check some dimensions and see what they could do. Two days later a new set of pins were in my hands - $0 cost to me. I even offered to pay them after the fact (called back to tell them how happy I was because I didn't expect to have a solution that fast) and they refused, saying it was their policy to make sure their customers are happy. Last winter I purchased an additional pin set for my K1200GT and one of the retaining pins was a little long. Wound up speaking with their GM, explained the issue (for which he apologized profusely) and next day a shorter pin was at my house. Can you guess what they charged me again?
Seriously, I would not hesitate to recommend them to anyone and I can't recommend the product strongly enough. For the same price of any of the other decent chocks on the market it's the way to go and as I mentioned, I still own a Baxley and Condor - now repurposed for other uses.
One last note - when I mounted the TRS floor supports (4 bolts for the floor plate) I drilled the front two bolts through the flooring and metal 'I-beam' for the flooring support. Rear screws went through the floor and then secondarily secured by strap metal across the rear screw points to 'sandwich' the flooring. I'm confident they're going nowhere.
If you have any hesitations about the product give them a call, explain the scenario/concerns and I'm sure they'll give you an honest appraisal and provide solid info/feedback without any BS.
