Shims are fine, but do try to make it look as nice as possible.
For the knee ammo pack you should really use cap rivets, because neither split rivets or brads are accurate. But at least make sure they are not pop rivets with holes in the middle of them. A solid head is required.
As for your missing D-ring, this is an oversight on my part, it's actually required for EIB, so make sure that you fix that ASAP.
You also have to have rubber or latex handguards glued to rubber gloves.