My babies are also in a glass viv with sliding doors. (It has a divider in the middle to keep them seperate.) Mine couldn't squeeze between the doors, but I did discover that Jubilee could squeeze her way into the door track above one of the doors. She couldn't escape from there, but I did worry about her getting squished if I opened the door not realizing she was up there!
What I decided to do was just house them in plastic shoebox size bins for right now, which happen to fit perfectly in their viv so that is where I keep the bins. I decided it just wasn't worth the aggravation of worrying about those tiny babies wedging themselves somewhere. I put the UTH (on a rheostat) inside the viv, under the bins, to maintain temps. I just centered it between the two bins and it's the perfect size to provide a warm side in each bin.
Once they grow a bit bigger I will turn them loose in the viv, but for now I'm happy having peace of mind.