Order the belt through another vendor. There are horror stories of the customer service at Inzer (taking months to get belts etc). I got mine through houseofpain.com (http://www.houseofpain.com/product/_...belt_10mm.html)
1) double prong is a pain to get on and off. Single prong is sufficient.
2) if you have any doubts about sizing, call them and ask.