btw: "23" you should give some serious consideration to 'roughing up' the outer perimeter of those tires to prevent flow separation - think dimples on a zipp wheel.

seeing as this is DIY, something to consider would be perforated vinyl film (similar to what they use for one-way printed window signs on stores and buses) with either 30/70 or 50/50 light permissibility. in the case of the disk wheel, a concentric ring covering the outer bulb portion would do nicely (but keep the center circle inside the bulb perimeter smooth and flat). and the case of the HED tri-spoke, basically the entire surface (outer rim, spokes, etc.). the vinyl is pliable and flexible enough that you might be able to overlay the entire side of the tri-spoke with one piece. and the diameter of the perforated holes is around 1.6-2.0mm so just about the right size (and depth) for a dimple.