Trained as a biologist, but have done research in wheelchair seating and mobility over the last 20 years, mostly while I was a supplier, but now, because of some need I have. I have been to Mexico, Costa Rica, and Viet Nam to fit donated wheelchairs to children with disabilities like CP, and other congenital anomalies that result in impaired mobility. I like to make it easier for those folks to get around. I am indebted to members of the Stack Exchange for helping me answer some questions that are a little out of my league.