We are going to build a hoop style house using a 4 foot posts set in the ground on the sides. I just need to span the area between the 4 foot sides. I know if I was building a standard hoop that 20 feet of PVC makes a 12 foot wide greenhouse. What width can I build with that same 20 foot sticks of PVC from wall to wall?

Simple math says 20, but I don't want the roof getting too flat. Our snow load here is rarely over 6 in and rarely lasts long.