While two of my daughters were able to fly our -6 tail dragger using just additional cushions, my other daughter is so petit that she needed more than that.
So, I used a thick chunk of model-maker's balsa, cutting it to the size of the rudder pedals. It was thick enough to stick aft, beyond the rudder pedal bars.
On top of this, I used flat-head wood screws to attach 1/2" thick plywood, as wide as the pedals but longer, so that they would be the same height as the pedals but hang down beyond the bottom of the rudder bars. From the side, these blocks then looked like a capital letter 'P", with the rounded part of the "P" actually flat as that would be the part attached to the metal rudder pedals.
I held these blocks up to the pedals and traced all the lightening holes on the back of the balsa, this gave me two spots where there was enough metal to attach the blocks to.
Then I used a drill press to drill backwards between the scribes circles, one hole at the top and one near the bottom.
Then, using a long drill bit, I held the blocks in place on the pedals and drilled through the pedals themselves.
After that, it only took tapping the holes in the pedals for the screw threads and off to the hardware store for the correct size screws that ended up being about three inches long.
I also oversized the tops of the holes in the plywood so that the screws would not sit proud.
Takes about five minutes to install or remove...