One shortcoming that many people feel the Sonex has is the standard cable actuated brakes. #604 had cable brakes and they seemed to work OK, but were never that stellar; #1374 would have better brakes.
Great Plains makes a nice hydraulic brake package that works with the standard kit wheels. It includes a T-handle lever and all the associated hardware needed for most installations. I wanted to use the center Sport Trainer controls and didn't want to use the supplied T-handle. I removed the Hegar master cylinder (Model 3520) from the T-handle and attached it to the Sport Trainer brake handle. The geometry was determined through trial and error, but the goal was to have the total travel of the brake handle match 3/4 the length of the master cylinder stroke. This produced a great feel to the lever and pleanty of brake holding power for a full power run-up.
I also decided to use larger tires to make operations easier off my gravel runway. My tires of choice were the McCreary Air Hawk 5.00x5 Tires, Aircraft Spruce PN 06-07710, and tubes were the Aero Classic Leak-Guard 5.00x5 Tubes, Spruce PN 06-00755. These are a great combination, but are much too large to fit in the standard wheel pants. I bought a set of RV-4 pants and modified them by making them wider.
The last modification was to weld two additional torque lugs onto the axel to ensure the brake mounting plate didn't come loose from the axel. One lug just didn't seem like enough.
Great Plains Brakes:
The cylinder is also availible directly from Hegar (cheaper too!):
Aircraft Spruce has Hegar parts also:
LEAF also has Hegar accessories:
NOTE: photos link to full size image