ohfour, trust me they'll fall out over time, even more so if you pop em out to take the rack off. it's just a matter of time.
dutchthrone: regarding the backrest, i had a similar issue, and come to find out the ventura rack works well for this. i'm still thinking about how to attach a cushion of sorts to it when i want to. it has a sticker that says its not a backrest, BUT works well so long as your passgener doesnt lean back with their full weight/strength. so work it has worked well with my girlfriend.