In general, 1” webbing is the standard for tying a Swiss Seat. Some people have been able to obtain 2” inch webbing
(
http://www.nrsweb.com/shop/product.asp?pfid=1847&deptid=1039 ) to spread the weight load at points of pressure. The 2” webbing can be more difficult to tie, you should always practice both on yourself and a volunteer “victim” to gain proficiency. The 2” is less convenient to carry around, but may provide a better option for some individuals.
Depending upon the need, skill and frequency of use, I would use a standard rescue harness or diaper sling. A Swiss Seat can come in handy and can be padded with towels, blankets, clothing, etc.
Pete