Here's simple math, that shows the cherubs, are not on top of the mercy seat, but rather to the side of the mercy seat.

Exodus 25:17 "Make an atonement cover of pure gold--two and a half cubits long and a cubit and a half wide.

So if the mercy seat, is two and half cubits long, that means, if the cherubs are on top of the mercy seat, their wingspan which the bible states are touching, would also add up to roughly 2 and half cubits, are less.

But, scripture states:

2 Chronicles 3:12 Similarly one wing of the second cherub was five cubits long and touched the other temple wall, and its other wing, also five cubits long, touched the wing of the first cherub.

So again simple math tells you since it's wings are 5 cubits long, this far exceeds the length of the mercy seat, meaning the cherubs are on the ends and to the side of the mercy seat. Therefore Ron's depiction, showing the cherubs on the end and to the side, would more closely match this description.