Not easy to do on the Kity, but finally got round to replacing the stock insert with this one.
It's made from 2.5mm galvanised steel, with a few spacers epoxy'ed onto the bottom to bring it up level with the table. The fit is tight enough not to need to screw it down to the existing fixing holes.
It would have been nicer to get the saw blade slot cleaner, but I had to use a grinding wheel to make the slot which isn't the most accurate of methods. Perhaps next time I'll use aluminium and cut through it with an old blade to get it more exact.