Length of bunks in quad bunk trailers

We're looking to buy our first trailer for our family of 6. We've been looking at used 3 tent hybrids, but aren't finding anything close by, so we're considering going with a quad bunkhouse instead. I'm getting a little frustrated by how rarely manufacturers list the dimensions of the bunks in their floorplans, though (unless I'm just not looking in the right place). My oldest son is 14 and already 5'10", and the next two aren't too far behind him (the littlest is only 2, so he's not outgrowing anything any time soon). We tried out a Rockwood Mini-lite with 72" bunks, and they're definitely not going to work for my oldest. But we've been in a couple of others where the bunks seemed to be a good bit longer. Is there some kind of standard length that most brands will have, or is it just different in every one? Does anyone know specifically about the bunk length in the Keystone Passport 2910bh? Is there any way to find the information on various floorplans without just calling up the dealers and asking them to measure (there are several we're interested in, but all 1 1/2 to 2 hours away, so I don't want to drive up and find all the bunks are too short)? I feel like I can't be the only one who needs to put tall people in bunks; the info must be out there somewhere!