I have a brand new gas insert that came with two sections of round 3" liner and a new chimney cap, but as you can see in the attached photo, the base of the new cap is a piece of flat metal, I assume to allow "one size fits all." The install instructions with the cap/liner simply say "Install cap to top of chimney," and give no other explanation. I've queried the company but haven't heard back from them yet, and wanted to get started. Does it seem right to assume that the corners of the base of the cap are cut out, as squares, and the four sides folded down over the top of the chimney tile, then screwed into place? Just want to make sure I'm not overlooking something obvious, before I cut. As an aside, the install manual does not address or show a drip leg in their diagram of the gas piping. Is that an oversight on their part, or is it not necessary to put a drip leg on gas inserts? Thanks.