I don't think there is an issue with how close it comes to the back as long as it doesn't actually touch the back so not to create a rattle and block the venting for the voice coil depends on the sub. As for a suggestion for a 10" sub in a .5 cubic foot box look at Boston Acoustics. I haven't installed one of their subs yet but, if they are anywhere near as good as their component speakers they are well worth the money. The dimensions should give you some extra breathing room as well with the 4.75" mounting depth.