Four out of five responses said to fly cut it flat first.
(Note to self, next time buy a thicker bar so there is more room for flycutting... This may be a bit tight by the time I get both sides flat...)
Now all I have to do is get a lathe collet big enough to hold one of my larger flycutters so I can do the whole block in one pass. One of the worst things about my Smithy is that the mill head uses an MT-3 taper instead of an R-8. Makes it a real pain and much more expensive to find tooling.
I don't think I'll have to much trouble with heat related distortion, I've set up the machine with a coolant pump using a soluble oil stream. Yesterday when I was fly cutting the rough cut end of the block I found the coolant kept things cool enough that I didn't feel any heat even putting my finger on the cut surface right after a pass. (What I haven't figured out real well is how to keep the cutter from giving everything within five feet a soluble oil shower.
I've hacked up a partial crude solution involving hanging cut up laundry soap bottles arround the mill head, but it's a real kludge and only partially effective.)
I do thank everyone for their advice.
Gooserider