This one was a challenge - how to align the wingtip position / strobe lights when there are no orthogonal surfaces on the winglets. I tried measuring, but without a straight edge, there was nothing to measure from. I set up a horizontal laser and aligned it on the edge of the wingtip. It was definitely NOT a precision job, but I think it is close enough that, at 2 miles away and at 145Kts, it should look OK. That gave me the line under the winglet. I used a carpenter's combination square to put some dots on the winglet an inch above the wing edge by keeping the laser on the edge of the square. Then I drew a line across the dots. It was all good, but not the right height, so I offset from that line a little bit more and drew another line. I put the gasket from the light on the line to make sure it would fit, and then crossed my fingers that the M5 rivnut was going to fit, too. Luckily, the stars aligned and so did the light, so I set up to do the same on the other wing tip. My goal was to get close to symmetrical, even though no one was ever going to see both sides at once (except at a distance). I ended up hitting my goal and getting close... I used the rubber gasket as a template, lined up the two holes on the line I drew, tried to get it a repeatable distance from the edge (lack of orthogonals hits me again...), drilled my #10 holes for the M3 rivnuts, crossed my fingers that I didn't strip it out again, and installed them (the rivnuts, not my fingers). I think it turned out OK. A suggestion to Sling would be to set up a jig in their factory for the wingtips and scribe a horizontal line across the winglet to make it easier for us builders. It will take some time to set up the jig for them, longer than it took me to set up the laser, but once it is set up, they should be able to mark each wingtip in just a few minutes rather than the 4 hours it took me! The wires from the lights weren't long enough to go all the way through the wing tip and to the wing, and I didn't want to be forced to try to make connections with my big hands inside the little wingtip, so I spliced in about 18" of wire using the super-cool heat shrink splices I used on the rudder strobe light. The hold for the wires was not big enough to cram all 4 connections through at once, so I shoved them through two at a time. If you're worried (and I know I was), I tested the connections for the lights both before and after I crammed the wire through the hole, and the lights worked fine once all was said and done. Just for fun, I put one of the wingtips on the end of the wing and lit it up. Yeah, I think it's gonna look good!