I recently completed a DIY CNC (Pictures in the Machine Gallery) and have spent the summer and fall tuning and playing with it. I had to use some shimming to get the spoilboard to be flat, (obviously some design-build errors), and had started to save up some money for additional tooling.
I came across a topic somewhere about spoilboards and the need to surface to help you get good Vcarving. I then looked at the size of my 1/4 inch tooling and decided I needed to look further, since I have a good size work area on my CNC, it would take quite while to surface my spoilboard. When searching for surfacing tools, all I was seeing was $200, $300 and higher indexable cutter prices!
That would not fit my hobby budget at all! Finally I came across a Whiteside 2 inch (1/2 inch shank) fixed tip spoilboard unit for under $60.00. I got it at carbideprocessors.com, but I am sure you can find it in other vendors inventories too.
Just thought I would pass this along, because surfacing with this 2 inch tool in my router was pretty fast and painless, but make sure if you are using MDF spoilboard, you have dust collection and wear a dust mask!