The Energon Pub

[Ramrider]

I've been studying my Cyb Soundwave, and there's a couple of ports I don't get. There are a couple of holes in the sides of his hand-held rifle, which I assume is so you can combine the two weapons if you want (if anyone has any other suggestions, I'm glad to hear 'em).
But I'm confused about the hole on his back in robot mode, and his underside in jet mode. It's slightly larger than the standard 5mm hole, since any post I put through it is very loose. I can't see any reason for it to be there, but it seems very deliberate. Does anybody know if anything's supposed to mounted there, or if he's designed to dock with something in jet mode?