I am just nine (my birthday was last week) and I am not very tall. I have a set of pedal extensions for my Lyon & Healy 85 Grand Petite. I live in the UK and ordered my harp & the extensions from Holywell Music in London, they are great. My dad will type the rest of this.
They are very simple and work well but you have to take them off to move the harp although Benjamin is too small to move his harp, he can take the extensions on and off. The only thing is that he can not rest his feet on the floor, some one suggested that it could be a good idea to make some kind of a box that fits under the stool and is curved around the pedals so the child can adopt the normal pose of a pedal harpist but Ben manages fine.