M.B.
Try weaving the mesh bumper in and out of the slats. It may help reinforce the ends so they are not as easy to pull off. I have always used the regular bumper pad, although I have considered the mesh kind. My son is 18 months now and I still use the bumper pad. I tried taking it off a few times but when I did, I would go check on him at night and he had stuck both legs through the slats. I always ended up putting it back on. Another alternative may be to stitch on some little ties at the same place as the velcro that way if it does come loose, it will still be tied on.
Best of luck to you!