Well, I found a killer deal on some used unknown brand of gutter mount bars (maybe Thule or similar "aero" bars). From all I read, the load capacity should be at least about 90 lbs. That will do for any of my solo canoes, the heaviest being about 45 lbs. It will certainly be fine with the 30 lb Wildfire.
I don't think I'd trust it with heavier loads though. If and when I decide I'm going to keep this Jeep long term (first Jeep I've had since the late '70's and only had it a couple weeks, so the jury's still out), I'll probably install a bolted on rail system from Yakima like I have on my pickup cap.