Good article on making pcb boards by THD:
"Through-plated holes are an absolute must, with solder pads on both sides. This makes it much harder for a
repairman to inadvertently lift a pad or a trace by overheating or from poor technique. The way that we have
addressed this is to start with boards that are clad with 2 oz copper, and in the through-hole plating process we
add another 2 ounces. This leaves us with traces and ground planes of 4 ounces, and through plated holes with
2 oz copper in the holes themselves. I have seen some other people start with 3 oz copper, plating on an
additional 1 oz, and I have not like the results I have seen. The through-holes pull out too easily."
http://www.guitaramplifierblueprinting.com/thd.html