915is oil temperature control

I would like to know if there is an approved method of controlling the oil temperature of the 915is,  thermostasis makes an oil control unit for the rotax that is approved for use with the 912 and 914,  but does not state it can be used with the 915.   This is the only oil thermostatic control that i have found for the Rotax.  Thermostasis is telling me that the oil pump for the 915 is larger than the 914 and therefore the thermostasis unit they have is not sized for the 915.   The 915 uses 1/2 inch oil lines and the thermostasis unit has 1/2 inch connections so it looks like it would have the proper flow for use with the 915.   I live in a very cold climate and need to find a way to control my oil temperatures during the winter.   My questions is anyone gotten approval from Rotax to use a specific oil temperature controller, and or is the thermostatis unit acceptable. 

thanks for the help