i found some rust today, a small 3" hole in the front drivers side frame rail. im thinking of just cutting it out and welding a new thicker piece in, how well would this hold?

 

That Will Turn Into A Much Larger Patch Then It Looks, You Will End Up Opening A Can Of Worms, Not To Sound Negative, Just Comes With Experiance, Build Some Cardboard Templates Of The Sides And Bottom, Then Make A Hole New Rail For Like 6 Inches On Each Side Of The Hole. Cut The Old Crap Out And Itll Be Perfect, And Use 16 Guage That Way If You Jack Up The Car It Wont Dent Like The Stock One Is Currently. Use Zinc Rich Primer On The Inside So Its Protected And Your Good To Go. OOH AND WHILE YOUR AT IT FIX YOUR FLOOR THERE TOO.

 

i was going to cut out both sides and the bottom of the frame rail with some 1/16 alum. plate, then strip off all the gunk and paint off the rest of it fix all the rest of the rust, then get some por-15 then finish it off with liquid grip tape, that stuff seals like none other...o yea, thats not the floor, its the spare tire well, i was going to cut it out at box it in anyways.