The Super Kaos Jr is not a resizing of the Super Kaos. It’s an original design of a 40 size Kaos published in RCM magazine, so look for the correct plan if you want to build it.
You have the choice of standard ribs or alternate, as detailed below:
These have a long leading edge for use with a notched diagonal leading edge stick as shown on the plan. They also have 3/8 x 3/8 spar notches for use with a big fat balsa spar.
These ribs have a shortened leading edge for use with a flat 1/4″ balsa leading edge stick. They also have 1/4 x 1/4 spar notches for use with hardwood spars.