Sparrow hawk oil cooler/filter

[HAWK PILOT]

I am installing an oil cooler on my hawk. I obtained the cooler from Groen Brothers. The adaptor that mates the oil filter to the engine block has two o rings on the block side but only one of the rings (the inner ring) contacts the block face. The oil filter side of the adapter just barely makes contact with the rubber mating surface of the filter normally used on the 2.5 liter subaru. Is it ok that only one o ring contacts the block. I assume that this adaptor is used on a variety of engines. Can I use a different (larger) oil filter so that I get a good seal? If so, any suggestions on the filter? Also does anyone know the new oil volume of the engine when using the positec oil cooler arrangement?
Thanks

[Mark Sanders]

I have a oil cooler on mine but not from GBA and had to try 4or5 different oil filters till I found the the one that worked for me. It is Bosch oil filter#3401 you might give it a try. as for the o rings usually you only need one per side two could cause leaks you may start with one and then go to two if it leaks at start up you will know in one second if it leaks shut off the engine. good luck.