Topaz,
we seem to have a very similar libary...
Thanks for the thumbs up on my (very preliminary) design.
As to the delta center section. yes, this will only work if enough vorticity is generated. At that operating point, the two outer surfaces of each wing will be deployed completely up, creating a lot of wing twist in the right direction. I think tip stall can be controlled, all the more so because of the low pressure side of the winglets should help in this respect. There are other measures one could take: small vg's on the control surfaces; those thingies that all EZE-derivates seem to sport on the leading edge of their main wing, etc...
As to X-Plane: checking out this product with plane models that I have flown for real, I'd say that it's pretty darn good as long as you stay within the linear aerodynamics limits. Stall modelling stinks. Other than that, I feel it can be used for conceptual/preliminary design.
I have other software at my disposal, but I don't like most of them.
bye
Hans