M.K.
I started using the crib tent on my son's crib when he was 20 months old in Dec. I LOVE it! Worth every single penny, as I'm sure it has saved him from a serious injury!!
As clever, stubborn and determined my son is, I can't see any way for him to figure out how to get out or tear it down. If I was going to try to tear it, I would grab the "honeycomb" pattern of the tent and try to pull it apart...but even then, I'm not sure I could tear it -- I think it has nylon threads.
We have a traditional crib. The specs on the tent said that we would be able to lower and raise the side of the crib, but I haven't been able to do so. Not a big deal for us, since our son stands up when we want to pick him up.
I saw some pictures with notes from a Mom on Amazon.com, showing how she used the tent with her convertible crib (since one side is higher). Here's the link. (This is the tent we bought at Babies R Us.)
http://www.amazon.com/gp/customer-media/product-gallery/B...
In place of trying to modify the use of this tent model, maybe there are models available for convertible cribs. I might try a specialty company, like One Step Ahead.
Be aware of your son's potential reaction -- our son was angry as a hornet for a couple days after we installed the tent!! But now he doesn't know any different and we are all happier.