While the wings are mounted on the plane and the ailerons attached, it's also a good moment to drill the wing tips.

These are polyester prefabricated tips that need to be trimmed to fit and positioned so that they fit nicely in the outer wing rib and at same time align with the aileron in neutral posiition.

The latter being the most critical in this process. You don't want you wing tip unaligned in flight as it may and will create a tendency to roll the aircraft.

A good tip when installing the wingtip is to insert some isolation foam cut to the size of the wing tip. While inserting in the wing, the tip will want to fold inwards without it. The foam make it easier to insert and to drill later on.
Just hold a foam plate next to the outer wing rib and trace the contours. It makes it much easier when doing the job alone to keep the tip from tilting down all the time.

First you need to cut off a part of the glass because it interferes with the aileron.
You have to do this on both sides. Don't cut them the bottom side in the same way as the shape is different on the bottom side then on the top.

I marked the cutoff area in red. The picture shows the right wing tip so you are looking at the top. Be conservative on your first cuts.

With the part cut off , you can now slide the wing tip all the way in. You may need to further adjust the trim to get the required gap between the aileron and the wing tip. The gap should be 1/4" as indicated on DWG09.
The aileron moves up a lot so the gap over at the front of the aileron has to remain clear.

Overall a nice fit

Here is a shot of the bottom of the wing tip. As you can see, the cut of the trim off is less deep here and almost comes close to the end of the aileron hinge bracket.

I'm quite happy with todays work. The tip aligns well. Tomorrow I'll continue with drilling it.

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I will go for the modification using nutplates and screws instead of pop rivetting it. I like the idea of being able to take them off if for any reason I need easier access to electricity wires or lamps in the future.