I'm one of those that only had upper C's installed and I have no fear that I will get a bend there at all. There were a couple of reasons I went with just uppers, though. First, and foremost, the TeraFlex gussets were the only ones readily available to me in the short time I had to get them installed before a wheeling trip. But they were a bit more cost-effective, too, at $35 vs. $90 for the EVO's or any other upper & lower sets. Had the Polys been readily available, yeah, I probably would've gone with upper and lower, but since they weren't and I had limited time, I went with what was available. And the manager of the shop where I had them burned on said he didn't really see a need for lowers anyway because he'd never seen tubes get bent downward at that point.
Do the upper and lower gussets make the axle look beefier? Sure. Do I give a shit? Not really. As long as they do what they're supposed to do, I'm a happy camper. Besides....who's going to be looking at my c-gussets when I'm wheelin' anyway?
Choose your friends & choose your enemies. But choose wisely.