Phil...
I can't help feeling that possibly the best solution all round is for you to either upgrade or replace your table with one more suited to dealing with large cutters. I realise that this may not be the most attractive answer, but there's a reason behind it.
Every off the shelf table is a collection of compromises, most of them governed by cost. From what I've seen, the net result is a table that isn't much good at anything. Adding a false top as Aragon suggests may get you out of a bind in the short term, another alternative may be to use a vertical panel raising bit, but this too means modifying your fence, making it much taller and stiffer, paying particular attention to keeping the fence square with the table.. even then, there's no guarantee that you won't struggle with it..
Personally, I built my own table based on Norm's design (the old one).. I've found that the table insert can cope with every size of bit I've wanted to use, I've plenty bit and tool storage built into the table, both aspects add to the overall mass of the table making it a very stable platform to work on, and the working height is just about perfect for me; very comfortable to work at for long periods of time...
Whatever method you opt for, you'll need to bear in mind that panel raising bits DEMAND a low router speed. These bits are taking off large amounts of stock in a pass, necessating minute changes to the bit height or fence position for each pass so as not to overload the router. Remember to work across the grain before you work along the grain to minimise the effects of tear-out, and always, always, ALWAYS handle the stock with either push sticks or paddles to keep you at a safe distance from the cutter....
