Im instaling a cooker hood and want to vent through a double brick external wall, Ive seen an extractor kit that converts the round vent to a rectangular brick sized vent so the bricks can be removed instead of core drilling a hole. Question is - would the bricks in both skins will be aligned so you can remove the inner and outer brick and and push the square plastic venting sleeve through. If the bricks are offset surely this would not work??