Phil,
Is your 20b p-ported? If so, it will idle rougher than a side-port engine. With that in mind, you would be better off to mount the oil cooler from the engine mount. Either way, you should plumb it with flex hose and steel fittings.
If you go through a lengthy period of tuning, you could damage your oil cooler before you get the engine tuned properly.
Mark S.
Lancair ES, PP 20B