Drolet install problem

[D_Bray]

I’m finally getting around to installing the heat commander and I have a few questions. I’m installing the wall thimble and I have double wall pipe from the furnace to the thimble. I’m using 2 45’sfrom the furnace to the thimble. It then converts to triple wall class A. I can’t get the dvl adapter from the stove pipe to the thimble to fit correctly. Would I be better off using the 90’s in place of 45’s. What should I do differently? The 45’s are not giving me enough angle to be a true 90degree fit.