Just saw your first group of questions.
-butt is a lil lower than the knees. referred to as "dump"
-6 inch! huge benefits!
-adjustability is very good. people have favorite chairs because everybody is different, and how we fit in things and become comfortable is different. Any adjustability in the chair will greatly add to how many people will be able to use it comfortably
-as close as possible, this is where your lexan guards come in. on manual chairs those are called "clothing guards"
-no real standard.
-most chairs have wheelie bars
-storage is good, compact is better. if it fits..........
-if they're in a chair you have given them the gift of mobility, they will move themselves under a shade tree with a smile on their face
-keep up the good work!!