Brian, BTW, I tend to agree with TUNY on wing section at the tips. Not necessarily for the same reasons as TUNY. Tip stall is likely a minor concern on these very lightly loaded bipes.

In my latest design, Delta, I went to some extreme in reducing tip thickness percent. My chord was very small already at 7" (thickness of around 0.55") so my LE radius became very small. That small radius (1/16") I believe is causing unwanted inconsistency in snap and spin exits. It's just too small a radius and is not allowing as smooth a flow over the tips as I am accustomed to.

My best wing design to date was on my Temptress which has a tip chord of 7 1/4" and thickness percent of 10. The LE radius at the tip seems perfect to me at 1/8". It's a very wide flight envelope with the best snaps and spins I've ever seen. Very controllable and minimal control surface throw of around 12 degrees for ele and ail. If I want faster, I simply crank in throw and if I want slower, reduce that.

Point is, if the tip actual thickness is around 0.7" for a chord of around 7" it appears to be a very good set of dimensions. A little thinner is probably okay for a bipe, but I wouldn't go overboard.

I've seen much thicker tips work okay too but the required throws go way up..... not necessary. One such set of wings is on my Aesthesis (14% based on local hotshot input) and I absolutely hate the wing response. Resorted to stall strips on the tip LEs to get some reasonable response