We're looking at installing landing lights on our Rans S6S. The ones offered
by Aircraft Spruce are a bit big, about 5" diameter. I'm trying to find
something a bit smaller but equally effective. Does anyone here know what
(if any) requirements a landing light has, such as beam angle, width,
brightness etc??

The Hella Micro DE Xenon looks like a really interesting option. Less than
3" diameter, low power (35W) but very high light output and resilient to
vibration. See:
http://www.hella.com/produktion/Hell...o_DE_Xenon.jsp

Anyone used this? Good or bad? Any alternatives that are equally small and
effective?

Thanks!
Rob