Updated SMA Jumper
Made several improvements to the Jumper we built for Cameron. The Video pretty much shows it all. I think this type of movement amplifying design can be refined to work for many kids even SMA type 1. In the beginning Cameron didn't jump but would push himself slightly side to side. Positioning Pillows or stuffing of some kind can be used to brace the body for stability.
The rough band/weight adjustment is made by adjusting the length of the main bands. The fine adjustment is made by adjusting the length of the rope in the center.
Looking forward I am planning to try connecting this to a track in the ceiling that circles our kitchen so he can walk/bounce around
Younger/smaller kids could use something like the Hugga Bebe. When cameron was small we would put him in the hugga bebe first then the jumper all while laying down. Then we pick the whole thing up and snap him in.
I would suggest getting the amount of bungee and adjusting the height using a weight the same as your child. I contorted and juggled poor Cameron many times getting it worked out correct for him.
Hugga Bebe support for smaller kids: (you may have to find a used one)
Bungee material: http://www.ebay.com/itm/261155228827
Eye Bolts http://www.ebay.com/itm/261155228827
Brass Snaps http://www.ebay.com/itm/261155228827
Step 1: Adapted Doorway Jumper (the Harness)
We started with a standard doorway jumper and removed the plastic part and spring. Younger/smaller kids could use something like the Hugga Bebe to help support them. When cameron was small we would put him in the hugga bebe first then the jumper all while laying down. Then we pick the whole thing up and snap him in.
Step 2: Assembly of Main Section
We placed Eye bolts into a solid part of the header spread apart as far as possible. We used a metal Bar with loops at each end to keep the jumper spread open. In each loop we used a quick link. (The more band and stretch you use the better it will work) Using one long section of band I tied off one end to a brass snap then looped through the quick links to a second brass snap creating 4 bands.
Step 3: Adjusting for Weight
Using a weight approximately the same as your child adjust and even the 4 strands till it has just the right amount of lift and tie off the end of the main bands.
Use some stronger band material to go between the two eyebolts in the header. Put a D ring on the stronger parallel band with a small rope going down to the metal bar. Adjusting the length of the rope allows you to fine tune the tension for optimal Jump!