Can I pick your brains? How would you solve this puzzle....

[Jonathan]

which is why I looked at supported rails...they be straight!

i'm open to siggestions though (I can feel a custom rig coming on!)

What about these ones? Maybe not the cheapest, but they are good with lots of wood dust around:

http://uk.rs-online.com/web/p/linear...PSF_346163|cav

Apparently you can get them directly from the igus site in the size you want for a good price. It's probably worth exploring a cheaper option first.
I guess it all depends on how many you're making.