I bought my RV-3 in 2014, the oil cooler was installed at the FRONT of the right side intake (when facing the prop spinner). I could not get my temps up much past 150 deg F on moderate days in California.
I purchased and installed the VANS oil cooler shutter and fly with it totally closed until ambient temps are over 90 deg.
Fully closed on a cool day I can easily get the temp up over 170 deg, never had any low temp problems since.
I dont see temps like you get in the midwest in winter.
I trim the position of the shutter to maintain around 200 deg oil temp.
On a 100 deg day i have it full open and I can see temps climbing out over 220 deg but it settles down at cruise.
My -3 also has a custom cowling and reduced air inlet (round shape, 4" dia) like a Sam James cowl or SR-22. Under the cowl is a carbon fiber plenum which seals to the baffles and creates excellent cooling for CHT's.
So I am probably moving less air with a better pressure differential but I cant support this with any engineering...It just works. And less frontal area is more slippery.....faster!
Phots by PM if interested.
My RV-3 is more fun on accident than your Cessna is on purpose