Hi Robbie... I have finished the brake upgrade to my Smith Cub and am very pleased with the results.

The Smith Kit came with Grove 61-1 wheels and brakes. They were adequate with the 8.50X6 tires and just OK with the 26" Goodyear tires. Once I put on my 31" Alaska Bushwheels I was unable to hold the plane during a 1800rpm mag check and needed more braking to get into short airstrips. Per your suggestion I upgraded to the 66-1 calipers. The installation was simple and straightforward. I have good clearance on the Bushwheels as the attached pictures show.

I am most impressed with the new found stopping power. I now have more brakes than I will ever need. I can perform a full power runup with no tendency to creep forward. I was never able to do that before.

My neighbor has a Super Cub with double puck Cleveland brakes with 31" Bushwheels and after flying his plane I feel I have more stopping than he does. 
All in all, a very worthwhile upgrade.

Sincerely,
Lou Furlong N46LF