Here ya' go...FAR 23.1389. As I am the person who normally rails AGAINST the FAR's I hope this minor transgression of quoting them does not cause anyone a stroke...
http://www.aopa.org/members/files/fars/far-23.html#14:1.0.1.3.10.6.102.29
What it says in a nutshell is the green (Starboard) position light must be visible horiziontally from 0* (directly in front of the spinner) to a radius of 110* (20* behind the wing planform). from that point you must be able to see the white tail position light...Ditto for the Port (red light). The lights must also be visible for 180* in the vertical plane (directly above to directly below).
Homebuilt experimentation is a wonderful thing if the result is an appliance that is the same or BETTER than the Spam-can fleet has otherwise it's simply better to use recycled aiplane parts. Innovation not Substiution.
JMPO here but I help lots of people with aircraft wiring and have had (and will continue to have) battles with builders to use the proper switches, wiring, connectors, etc. instead of the Autozone fuseblock and wiring.
A minor cost savings now might come back to bite you later if you decide to sell...if you used non-avaition lights, wiring,etc. a buyer might wonder what else did you scrimp on...nuts and bolts???
Chris