Careful there--IIRC, he said he drove around for a year with the full load screw turned up, no IC, and he eventually destroyed his cylinder head (OM603, presumably with a late model #17-#22 head) during the warmer temps in Summer. Tread carefully, but, since you've set up a pyrometer, and will measure delta-T across the IC, you should have a better understanding of how efficient your particular setup will function. I suspect the cast iron head 617 will be a tad more forgiving than our 603 primadonnas.