I like the idea of the plastic insert. I have made a table out of 15mm MDF which is a little bit larger but the same shape as the cast iron table. I start the scrollsaw and cut a single line into the centre of the wooden table. When the wood is in the correct place I stop sawing and use double sided tape to stick the wooden table to the top of the cast iron table. This does three things: It gives me a perfectly flat zero clearance table. It is cosiderably warmer to use in a cold shed in the winter because your hands are resting on wood not cold metal. It also allows me to use a new section of the blade so when I've been cutting and the blade becomes blunt I can slide the wooden table onto the saw and all my work is raised by 15mm so I'm cutting on a new section of the saw blade.