I am a huge fan (almost 250 lbs.) of raised beds and my first set will
soon be nearing the end of their life. I have a welder in mind who
says he can build some simple raised beds out of 3/8" or 1/4" x 12"
metal. Has anyone ever tried this? The benefits are obvious, and I
don't see an obvious downside, except for these issues:

Do the sides get too hot and fry the soil and whatever else comes in
close contact? and

Perhaps they should be just a little larger so the new bed can snugly
fit over the wood, thereby keeping an insulating wall between the
metal and the soil?