Do I need an Oil Cooler Thermostat?

I wouldn't call that redundancy.  It's not like one system can take over for a major problem with the other.  

Many coolers  and radiators are welded back to back and aren't seperate. If seperated one may get better air flow cooling than the other so you could apply the aluminum tape. You're looking for the temp to be in a better range so if you taped one and not the other could happen. That said if they are too cool to start with then usually both coolers are too cool and not just one. Owners have been using aluminum tape for 2-3 decades. The Flight Design folks use it all the time in the colder months. I used it here in Tucson, AZ every winter with great results. Cheap and easy to use. Start with a 2" piece all the way across and then go from there. If you live in freezing temps then you may need more. For us in Arizona where the temps can be cold enough then one piece is usually plenty to keep oil temps in the 200's.

Tyler Hathaway wrote:

I wouldn't call that redundancy.  It's not like one system can take over for a major problem with the other.  

The engine can run at lower power with a coolant leak but not without oil, right? Or am I off base here?

A highly respected (and famous) Rotax expert told me that there have been documented instances of engines running for extended periods of time without coolant--not that I would ever want to try it.

I agree, you can run for a bit after losing coolant but not without oil...  how does that make for any "redundancy"?