So I bought a P61 off CL to replace my Magnum Baby. One problem I'm running into is the difference in exhaust height between the two stoves. It's 17.25 for the Baby and 9 for the P61. The exhaust pipe I have is Duravent. Seems like the pipe sections on my indoor vertical rise are set lengths. Is my only option to move the wall thimble or is there a way to customize the pipe length of the vertical rise? Thanks!