Hi Dave,
My current wings (Midrex) are 10% at the root and 8% at the tip ,with chords of 345mm at the root and 190mm at the tip. (bottom wing - top one is slightly smaller)
I'm increasing the root chord to 375mm and reducing the tip to 165mm with thickness at 10.5% and 7.5% respectively. I'm going from a straight TE to a 50mm rear sweep of the tips. Span increasing from 1.75m to 1.775m. I may put some fencing on this ,but if I do it will be mostly on top of the top wing and on the bottom of the bottom wing - this will mostly be to enhance stability on spin entries by preventing top side span-wise flow on the high wing. I may develop the strut mounts into fences also - they lend themselves to this development I think - but this depends on weight.
Generally, while trying to get lighter wings, I'm trying to enhance yaw stability and to 'centre' the drag and mass some more. This should also be a little more sprightly while being better in the wind. I started out ,in my thinking, with an elliptical wing but there is no rib cutting service here. I could have sent off for them but was afriad of where the weight would go and time and money are limited.
Anyway I was going to do this for performance but I'm not too keen on the look.
I decided on a straight taper and this is something that I can do myself in foam. The increased taper, once done properly, should help with overall stiffness and in particular give stiffer tips.
If there is any movement in the tips ,due to play or flex, the model will misbehave in pulls,pushes and snaps with wind complicating this further. I have been there !!
Thin sections work well once they are not too highly loaded and the loading is way down on these bipes.

Brian