BMatthews,
Thank you for your contribution, I compared my choice of Clark y against the Selig 4233 using Soartech vol 8 data. The Selig is 13.6 % thick vs Clark Y at 11.72 % so a win for Selig in terms of wing strength with like for like wing spars.
Surprisingly Clark Y is slightly more cambered (3,55% vs 3.26 %) and drag coefficients are on a par at Reynaulds no.s around 100K and above, the Selig has a slightly greater max Cl of 1.25 vs 1.2 .
From a practical build point of view however the ability to build the Clark Y version direct without some form of Jigging is the clincher,
You also gave some sound advice re engine/ motors being tractor mounted vs pusher on engine pods, I have given this some thought and have taken some inspiration from here
http://www.outerzone.co.uk/plan_details.asp?ID=6948 a Mike Pastro design with a single pusher motor. This has the advantage of only 1 motor and speed controller required and the thrust line will not require any offset whereas the high mounted pods would.
This of course limits the size of prop I could use, perhaps go to a 3 Blade?, not too worried about motor weight at rear as possibly 2 motors on the pods might have worked out the same moments around the CG.
The Key thing is to build it 8lbs or less flight ready, Mikes version was 7lbs with fixed gear, 8lbs with Pneumatic retracts for a 57 " span version.
Henry