I"m using a standard specifcation (ADSK IMPERIAL) to create some PVC Drain, Waste, and Vent Pipe. I know that schedule 40 pvc pipe at 3/4" diameter is an available product, but I can't seem to figure out how to change my settings to allow me to use this size pipe. The smallest size available is 1-1/4" diameter. How do I change the settings to allow the smaller pipe?