I mount mine directly below the trans. No fan, no gaurd, no problems. I've been running them there on my VW's since the 1980's. I don't do any off roading, so I haven't had any problems.
I like mounting engine stuff to facilitate removal of engine and components as a package. With cooler mounted beneath trans and filter mounted on engine, it's lots easier to R&R motor without breaking into oil lines or removing lots of external stuff. I just remove things like oil filter, cooler, coil, etc. along with the engine.
Greg