I don't understand the need for a reverse flow on such a small rig. RFs are typically used for large spans (towable rigs) and have a solid plate tacked in below the cooking surface. At the Highland size, this is largely a marketing ploy: similar results can be obtained by using tuning plates (4x16x0.25) that float under the grates to even out the heat in such a small space. Take a look at Horizon's backyard smokers: Horizon are the Davidsons. The Davidsons are who started Oklahoma Joe in Perry OK, sold to CharBroil, and OKJ are now being pumped out of China. None of their smokers have a RF stack on them, unless it is a special order, and there's a reason why you don't see one: it's really overkill and unnecessary. Nor did you see them prior to them selling out to CB.
Similarly, if you want to cook something hot and fast, you don't have the flexibility with a RF rig like you have on a conventional by moving the tuning plate(s) out of the way and putting what you want next to the firebox. Glad it worked out for you, wc, but I don't see the need. My $0.02.