Hey I hope you guys can help my dealer is clueless. I bought a harman accentra from my local fireplace dealership along with the zc box and vent pipe. When I tried to install the 4 inch L vent pipe that he supplied it would not fit through the hole. The hole on the zc measures 4 1/2 while the L pipe measures 4 and 3/4. Did the dealer give me the wrong pipe? I read that L and pl are interchangeable but maybe the dimensions are just slightly different? Do I need to return the pipe?