Hello again Clyde/Eugene - (not too sure what to call you) - I attached my spare Triton router table to my series 2000 Workcentre, and I understand your problem - sort of. Firstly, it appears that they haven't actually made proper provision to accommodate the series 2000 router table on the series 2000 workcentre - seems strange, but perhaps they were more set on accommodating the new router table, the RTA 300 - can't say for sure, but maybe someone else with more knowledge might chip in.
However, you can certainly use the router table on the workcentre. My router table does sit flat on the workcentre, as you will see in the attached picture. The red tabs at the back lock into the rails, which prevents upward lifting, but no provision has been made at the front for this, and the table can still move backwards or forwards if sufficient pressure is applied. As long as the router on its mounting plate is properly located and restrained on the underside of the table, you should be able to use the setup without a problem. If the table tends to move along the rails in use, one can use 2 small clamps at the front, as I show in the picture. But of course, the one clamp could be in the way of a larger workpiece. If this is the case, remove both clamps, as using just the back one could slightly distort the table.
You mention that your table is not sitting flat on the workcentre - is it rocking on the router mounting plate? It should just touch this plate to apply slight downward pressure on it.
Let me know if any of this is of help to you.