Clint,18.5 was the only option for a very long time, it's very versatile
1) put the fire grate & charcoal ring on the lower shelf to grill on
2) put the grate right on the fire ring & cooks the best steaks I know how
I've never cooked on a 14.5 but judging from the pics I see here a lot of people love theirs...as evidenced by the thick buildup of smoke & grease
This sounds interesting and good. Do you have any steps, photos, link?