It was not suggested that an 11-4 is "just right". As you will note, if you re-read the post, there are suggested limitations on the 11-4. Aside from that, there is a significant difference in performance between an 11-4 and a 10-6 -- while they have similar power loads, the 11-4 produces substantially more thrust than a 10-6, & the greater disc area is particularly important with a bulky, draggy airframe like the Kadet MkII. If the airframe had been much slimmer & cleaner, the 10-6 could be a good choice -- but not for the Kadet. Additionally, TT only recommends the 10-6 as a break-in prop for the .46 Pro.