Colyn, you're right.  I was using the CHT as a benchmark for whether I was LOP or not, but not how far. 

After trying it again with the lean find mode on the EDM-700, I now see that the spread is such that I can only get the #4 cyl to 10deg LOP before the engine gets close to quitting, because #1 and #2 are so much leaner at that point.

So, as it turns out, close, but not cigar.  ROP it is, then!

Keith