I'm in the process of doing my own install, and have ran into an issue. I have to offset my stovepipe to keep my wall clearances, but I'm not sure which way to go. I had planned on using two 45 degree elbows, but that won't give me quite enough. Would it be better to use one set of 90's, or 2 sets of 45s? This is for single wall stove pipe and a top-venting Appalachian 4N1. Thanks!