Positech Oil Cooler

Hi all,
I bought a Positech oil cooler (P/N 4211) for my RV-4 (O-360 parrallel valve) and I have heard some people say it doesn't do the job all the time.
Does anyone have any experience with this cooler in an RV-4?
Most of the people I know have a problem getting the oil hot enough in the winter here in the midwest

How about this.

http://www.vansairforce.com/community/showthread.php?t=43742&highlight=oil+cooler+comparison

POSITECH OIL COOLER

INSTALLED THIS COOLER IN MY 0-360 RV-4 OIL TEMPS IN THE 220 RANGE REPLCED WITH HARRISON-STEWART WARNER STYLE TEMPS WENT DOWN TO 180-190