I have a Ryobi RE180PL router that I'd like to temporarily put in a
router table. I'm building the table myself, with the intention of
putting a good (ie. Hitachi M12V) router in it. In the meantime, I
need a cheap way to attach this Ryobi without wasting a $40 insert.

My plan for the future is one of the Rockler (or similar ) aluminum
inserts for the big router, but if I cut a smaller hole for now and
used 1/2" plywood as an insert, would it work? This Ryobi,
unfortunately, has only 2 screw holes to attach to a plate, so the
hole pattern in a good plate could not be used with another router.

The cheaper the better for a temporary fix. Any suggestions?

Rob