Thanks for posting that link Lowell... and it's also corrected my spelling !. I chose these wingtips because I knew they reduced drag due to W/T vortice reduction and I think I read somewhere else that they also give you an effective increase in Aspect Ratio (beyond the physical wing tip-to-tip span measurement). But Jim, I'm interested in your comment somewhere else on the forum that you tend to get a bit of float on landing with these tips. I'm about 4 weeks off finishing my build and I'm interested to understand why that would be happening before I start on my phase 1 testing. Is your approach speed a bit high or is it just a natural aerodynamic characteristic of this type of tip ?. i.e. greater ground effect due longer effective wing span ....