Hello is there anyone on here that has used 12" (neutral) extension boxes on a 1989 Fountain Fever flat bottom? I have standard Imco sport master lowers now. They are 1:36 standard length and I need to go back to 1:50s So now is the time to figure out if I need 2" short lowers? I don't mind changing my gears but I would like to know some of your thoughts or what worked best on your older flat Botton Fever.