When I was a kid, when we needed a roof my dad would put a second
course of shingles over the first, if the plywood was good. Never
more than two courses of shingles. Now I need a new roof, and all the
estimates I get are from contractors who want to rip off the single
course of shingles I have and put new felt, etc. Is there any decent
recent for this, or are they just trying to make extra money?

Thanks
KM