Ollie, thanks for 'doing the math' there. Pretty interesting stuff. That is the first time in a while that I have seen anyone go at this problem (fast HalfA's) using 'true' engineering principles.

I have been building half-a pylon racers since the late eighties (took a long break off in the late 90's), and fly with a good friend (Spindoctor) who has built many more halfA pylon racers than me, and build some of the best I have ever seen. (The planes in his HalfAst series are something to behold)
We got to talking about the High vs low aspect ratio wing idea last weekend. We talked/debated which was best-high or low aspect ratio. We were both at the first pylon (40size) events when the first 'long' wing planes came out from guys like Jim Katz and others. We talked about how well they flew then. Now all .40 size planes use a relatively high aspect ratio wing.

I based my latest attempt on those ideas. A picture is below. Though this plane looks large (34" span), it has a very thin wing at 6% and a pretty high aspect ratio wing for a half A. I built it this way even though it was completely alter to my prior experiences/thoughts.
Well, what is my point? ---This plane is much faster than any HalfA pylon racer I have ever seen before. The difference is striking. Additionally, the airplane flies through the turns instead of mushing. Speed loss is negligible.
There are other more practical benefits also. Smaller spans produce harder-to-see airplanes. Oftentimes, they are also twitchier on the roll axis. High aspect wings seem to be groovier, and smoother overall.

These are just my experiences, but I feel pretty strongly that they have pointed me in the direction I will go for a while with my (pylon) designs.

Best of luck with your next design Painless