I have a question regarding the degree of angle I can use on the 8 inch chimney pipeing for a Tarm solo 60. I noticed when I was shopping for Class A pipe that they did not sell a Class A 90 degree elbow. Is 15 degree elbows the largest offset approved for chimney pipeing? Can I double the 15 degree to make a 30 degree? I have to come out the back of the tarm and angle up and to the left for about five feet and then somehow go vertical into the Class A tee? Is a 90 degree too much angle?