Ed Wischmeyer wrote:
To get
low induced drag, you need the sum of all lifting surfaces to have an
elliptical lift distribution.

Lemme display my ignorance here. I always thought that the elliptical
lift distribution minimized wingtiptip effects. That being the case
(ignoring the wake of the canard for the moment), then each wing should
have an elliptical lift distribution. When you toss in the wake effects,
is having the sum of all lifting surfaces give you an elliptical
distribution a handy approximation, or is it what you really want from
first prinicples?

The canard usually has a much smaller span than the main wing. Subtract
its elliptical load from the overall elliptical sum and you end up with
a really wierd load distribution on the aft wing.