On my RV-8 with an IO-360 Angle Valve, I've had very good luck with the stock Van's Niagara cooler mounted to the right baffle:
I know of an RV-6 with an IO-360 that also has the oil cooler in this location with good results. FYI, my oil temps typically run 190F in cruise, 210F on an extended climb on a hot (100F) day. I did see 230F once during an extended climb when taking off after a short lunch stop from St. George UT. In this case, the engine was already heat soaked from the previous flight. Lowering the nose during the climb to get the IAS up to 135 knots brought the temperature right back down. Also, my CHT's run extremely cool with this setup (330F @ 75% power cruise, always less than 400F during long climbs).
Skylor