Dene; It sounds like you've already got the info you need to source some disc brakes for the Sonex. However, if for some reason you want to retain cable operation instead of going hydraulic, there may be another option. Pietenpol builders have successfully used mechanical disc brakes from go-karts (Airheart and similar types of brakes). They use the cable pull action on a lever to rotate a cammed wedge which applies the braking force to the disc.
Here's a typical one on Amazon.com (Northern Tool), $30 each: http://www.amazon.com/Airheart-Go-Kart-Brake-Disc-6in/dp/B000ETZEJE You would have to find a suitable disc that you could mount to the Azusa wheels (motorcycle, kart, etc.), then devise a mounting point for the caliper on the gear leg. Oscar Zuniga Medford, OR
