I just had a patio cover installed and now want to add a ceiling fan. It is 16' wide by 10' deep and has a 3-1/2 x 3-1/2 inch sheet metal beam running from the roof to the edge (10'). I was told that the beam was strong enough for a fan, but how do I mount it. It'll be on a 4" down rod. The ceiling boxes that I've seen fans mounted to are larger than 3-1/2 Inches and I hesitate to just screw a 4" octagonal box to the beam. What other mounting methods are available? Thanks for your help>

got a quick question my 3 year old was throwing this ball around and knocked down the glass cover so while trying to screw the cover back in and noticed the fixture was very loose so started to turn the fixture to tighten (there was a center bolt hopefully for tightening) and after about the 5th turn the was a spark and no power to all but the master bedroom and the living room and garage so turned of main power with flashlight in mouth unscrewed the fixture and noticed nothing except the ground wire had twisted apart so pigtailed the ground wires and turned the main power on but when I went to the bedroom and flipped on the switch all the light in the mentioned above went out like I tripped the circuit what is going on and any ideas on how to fix it Thank You Robin Mays