Thanks rogerw for your experience with this issue.  I'll save your post so I can check out the direction of the nipple and maybe re-orient it and try the washer trick you mention.  I live a long distance from the farm where the tractor is, so it isn't as simple as just stepping outside when I have a moment to check it out.  For now, I have several layers of aluminum foil wrapped over the top of the fill cap and wired onto it (just under the edge of the cap), so it doesn't fall off.  Not classy, but it keeps the PS oil from spraying up into the air and onto the operator.

Buck's550