If you're NOT going to be swapping boards often, I've done this before:
Solder 2 wires onto the jamma board for the pins you're missing, slide them through the jamma connectorso they stick out the other side. Voila.
If you need to swap boards often, then pulling and pushing the wires in and out of the jamma adapter all the time just SUCKS, so don't even TRY IT. But if it's a permanent thing....