I also had high (230 in climb was my step climb cue) oil temps on an IO-360 injected, 9:1 piston, electronic ignition engine. After many failed attempts I bit the bullet and retrofitted an SW 10599r oil cooler to the same spot on the rear baffle. It required enlarging the hole for the cooling air. Problem is now completely solved even on hot days doing slow flight for a half hour at a time.
And if anyone asks why I would do slow flight for a half hour, it's the nude sun bathing colonies that my flight instructor always was trying to get me to see "if you just fly slow enough"!
Jeremy Constant