Russ, I have flattened hundreds of Paulson chips with about a 95% success rate (not so much with ASM chips, though). "Success" for me is defined as having a rock solid stack of 20 chips with no wobbling whatsoever, not just the day of the flattening, but a week later. Here are a few comments from my experience...
I realize your oven won't go below 170˚, but I strongly recommend lower temperatures (even with Paulsons), and use longer times if necessary.
Your c-clamps are a MUCH better choice than ratchet type clamps. However, realize that you can apply a VERY high clamping force with the c-clamps, enough to squash the chips, especially with the high temperatures you're using. I recommend tightening the c-clamp on the chips JUST ENOUGH to squeeze them flat.
Don't put the clamped chips in the refrigerator. Period. Just let the chips cool to room temperature on their own. This requires patience, as it sometimes takes more than an hour, but I have found it makes a HUGE difference in the success rate.
Also, while the chips are cooling, especially in the first half hour or so, check that the clamp is snug every 10 minutes or so. Again, use just enough force to keep the chips flat while cooling - don't over-tighten, or you can squash the chips. As the chips cool and contract, they get loose in the WOOD clamps that I use, though I'm not sure if that will be the case with your METAL c-clamps.
I know this post is about flattening Paulsons, but I want to caution everyone that contrary to popular opinion, ASM chips are significantly softer than Paulsons. It is VERY easy to ruin a clamped ASM chip in the oven, even at temperatures 120˚ and lower. Specifically, the cross-hatching gets partially mashed flat, and worst of all, the sides/edges of the chips bulge from the chip being squashed, even with a minimum of clamping pressure.
Hope that helps. Good luck!
(calling Mr. Cheddar...)
I'd suggest moving this post to the "Poker Chip Maintenance" forum, where I have a thread on the same subject:
http://www.pokerchipforum.com/threads/flattening-warped-chips.3903/