I will say being a bike shop,and dealer for many bodywork companies,it would be no use to just make one size cause the market you are entering is a conscious market.There are guys that race and street ride with 6 & 8 inch over tails.you then have guys that are straight racers that have 8-10-12" over setups that they continuely switch around.Prices and how fast you can get them built will determine what moves.