Brent, I have noticed that problem with a lot of the MB figure kits. The box art work would have you expecting flak jackets/vests on the figures. The one figure looks like he was cloned from the old Tamiya M113 kit, especially the undersize helmet which seems to be hit or miss with many model companies. After discovering for myself the failings inside of the MB figure sets I have pretty much avoided them. But their box art is very inspiring.
The missing flak vests was annoying; I thought of using the DML figs with flak vests, but I didn't have enough for all three and modifying the two that I have would have taken this project from "fun" to "annoying".
I checked the helmets and they are about the right size. The heads (or at least the tops of the heads) may be too big. I didn't trim the tops, so the helmets may be riding higher than they naturally would, making them look smaller. They have a half-assed attempt at the crinkled camo cover.
Not all MB figure sets are bad; some of the modern ones are OK. One common annoyance (which they're slowly correcting) is that the figures never quite matched the boxtop artwork, especially when it comes to included gear. This was a recent kit, so I don't know what happened.
At least they're better than the Trumpeter PMC figure kits; even wargamers would probably find them out of proportion.
The M151A2 comes with two rear corner antenna mounts, but only call out for one antenna. the second one could probably be used as the aux. antenna, but I sure didn't use it (and it wasn't called out in the instructions).