Hi K.,
Wow, I feel for you...that totally sounds like something my son would do as well. And, if your son is anything like mine, he is strong, sneaky and will find a way to do it no matter how many times you tell him no. Add on that this is a very dangerous situation, rough stuff. I had two thoughts.
First, I have to agree with another poster that there probably is another option for splitting the boys up, just maybe not an attractive one. At this point, one of those beds would likely be in my room by now.
But, if you can afford it, there are also monitors that go under the mattress that alert you to when they are out of bed (sometimes used for the elderly). I have never researched them on my own, but I bet if you check out google you could find something. I ran a google search on kid out of bed alarm and came up with a few results, including http://www.dynamic-living.com/product/fall-guard-alert-sy.... With this solution, he would never know why you know that he is out of bed but you could catch him in the act. That is always the best way to stop any behavior!!!
I wish you good luck, this is a tough one!
D.