Well, I rode it for a month or so, rolling it off a few curbs and over potholes and speed-bumps with my 220 pound butt planted on the laid-back seat. Haven't had any worries about creaking, flex or bends yet. The bent extensions are thick-wall 1/2" tubing and those delicate looking uppers are solid 3/8" rod. The seat stays are under compression, and are straight runs with no bends, so there's little chance of them deflecting. One of the design concepts behind this bike from day one was that it should look like there's barely enough frame present to hold the bike together, so it sounds like I've done my job.
the crank and the tank looks fabulous! 
