Tell us about yourself!
a cheap add on would to be use nylon corded up with some sort of heat device to heat heat the nylon. see MIT technology reviewto add a synthetic muscle to boot , and use a used inline skate boot( i think was recommended) eliminate as much metal as possible.
i am not saying you did not do an outstanding job being resourcefull.what i am saying take guidance from the community here and make them more usable and comfortable. I am trying the same as you but making parts on a 3d printer using other designs like the lab at MIT.Look at Oscar P with the chetah carbon blades or the jumping stilts.You should be able to make a more powerful runnig boot wtih same budget. Do you have maker club by you, we have a few in orange county. the more carbon fiber you can use instead of metal , the lighter and faster the boot/ stilt
Are you working with or duplicating the original designer, he made a bunch of prototypes that look better then yours. If you want to make look better, faster run , you need to work with lighter materials or your just copying the jumping stillts.$150 on ebay.Whats your objective to run faster, longer ?, use less energy, more then the calf muscle needs to be augmented, a knee and thigh linkage also is needed.