Mine is on the inboard access cover. In the shade and out of cooling air and exhaust gases. I thought there is one more advantage: Replace the cover and no extra holes in the plane in case it will be removed one day or relocated.
RV-7 flying, IO-375 w. P-Mags, 200RV Prop
RV-8, IO-375, P-Mags, 74RV Prop, flight testing