[aerohead]

Lots of good suggestions by members and I'll add what I did to the soup.Fortunately for me,the Toyota had all kinds of frame rail penetrations already in strategic locations.The holes were large,however by filling the big holes with suitable flat-washers,then capturing those from both sides with even larger flat-washers,I was able to attach hangers for my belly-pan by through-bolting, without drilling or welding.And a note of caution: the frame is hardened steel and if heated,can loose strength,and yield at a lower load.If you simply have to weld,use TIG or MIG to localize the heat and keep some wetted heat sinks surrounding the area to conduct heat away to the environment.Remember too that you have the potential for fire and explosion if any part of the fuel system is compromised.Angle metal can be attached to the hangers with bolts.I recommend nylon-insert nuts,as they cannot inadvertedly come loose.The angle metal can be drilled for skin attachment,and speed-nuts,from auto parts or auto refinishing supply provides an anchoring point in lieu of Dzus fastener weld-on backing plates.Also,light metal angle can be pop-riveted to the aluminum sheet to create modular panels which can be attached as a unit.I've used this since the 1970s and never had a failure.Aluminum is prone to fatigue fracture and needs to be securely fastened.Big fender-washers are handy at attach points,as they distribute fastening force over a broad surface area.Whatever method you use,just make it tough and strong and avoid some of the stupid moments I've encountered over the years.