Hey Tom,
Geez, that running light is a freakin' joke... (grin)
My teak handrails, along with my dorades, and tiller, are the only items of exterior varnish on my boat... Pretty minimal maintenance, they live under covers most of the time, of course...
If you do go with varnish, you might try what I did... I made a sort of "spacer" from 1/4" white starboard between the handrail base, and cabin top. Routed/gouged out a bit of the underside, as well, so it serves as a compression gasket for the sealant. But when it comes time to re-varnish, it greatly eases the process, I don't have to bother with the PITA of taping around each base, which doesn't work very well with a non-skid surface as gritty as mine, anyway... Whatever varnish I do smear on the Starboard doesn't adhere very well, so it can be easily removed after going around the joint between the rail and the Starboard with a razor blade...
best regards,
Jon