Yeah, every time I see a horizontal filter on any engine I wonder "what the hell were they thinking?"
I have mine mounted vertically, screw-on flange pointing up so that when I unscrew it, it hold the oil in it with minimal leakage/spillage. I also pre-fill the new filter with oil when I do an oil change so there is never a massive air bubble in the system at first start-up.
I bolted my mount to the body frame member that forms a square horse shoe around the engine. It's positioned so that hose and valve cover access is easy. Been there for 20 years and the mount failed last year (it was a flimsy aluminum plate affair that I had made) but other than that has been trouble-free.
I documented my set-up on here years ago:
https://www.speedsterowners.co...-1-mechanical-layout
But the layout photos are long lost (Photobucket started charging for use) so here is the placement of the cooler and filter in a series of photos - It works great. Just to be clear, the filter mount itself has been bullet-proof. The piece of diamond plate angle stock I used as an adapter was too thin and not up to the task, so it failed and was replaced by a steel equivalent - That's been fine. Be careful of where you mount the filter and hoses so that valve cover access isn't impeded.
