I've got a DD 52 Ferris WB 2007 model. I was wondering if anyone has tried to reto fit the new thumb controls that appear on present Ferris Comfort Control DD WalkBehinds to the old Dual Drive Ferris walkbehinds. I sort of need or would like these controls to aid in climbing very steep hils, straight up. Most of the time I really have to push the joy stick fairly far forward and then push down on the control handles to get her to move up the hill. I was hoping these thumb controls would help in easing into hills. Soooo....anybody retro-fit these thumb controls to older Ferris's?