So I ended up pulling the trigger on the 16" (small) frame Diamondback Axis last night, after a frustrating go-around with the idiots at Dick's. I winced while paying since their manager said their 90 day return policy is ONLY if you don't ride it, which was contrary to what the dweeb with the headset told me 2 minutes prior.
I tried the 18" frame out, and that was an immediate no-go. Even with flat tires and up on my tip-toes, I could not straddle the frame without having my plums split in twain.
With the 16", I have about 3/4"-1" of clearance or so. I was a bit concerned that the frame was too small once I got it home. As I sat on it, I felt a bit squished relative to my knee/leg placement, and it seemed as though toe clipping would be a bit of an issue. Hopped online and found a nifty page on basic adjustments as to what your position/feel should be. Moving the seat up and back made a world of difference. Needs to be moved back even more, but no longer feels as though it will be too small. If the final seat adjustment doesn't do it, I'll take the damned thing back. I just started off way too low - I suppose being programmed to ride BMX as a kid where you never sat on the seat unless you were coasting down the street, so you just put it as low as it could be. The bike is probably a BIT on the short side front to rear, but with my build, the only other option would be finding a bike with a short frame and a longer, more radically raked (lower in the rear) top tube. However, I've still got some forward lean on this bike, and if I had to, could always push the handlebars out some.
My one big disappointment with the bike is the worlds SHITTIEST plastic pedals. Any recommendations for a low profile, grippy pair of no-clip pedals that won't break the bank?
Oh yeah - I never gave much thought about it, but never thought the front shocks on these things would be so damned soft. Being a fatass doesn't help. I suspect I will ride it with a fair bit of preload until parts go flying, and then upgrade to a "real" front shock somewhere down the road.