Any 20K flight in J would earn double the PQM and as such result in 40K earning. So, something like NYC-IAH-TYO-SIN is 22+K miles, and 44+K PQM in J.

IAH-NRT on NH is pretty nice, I'd gladly do it again. Prices may be pretty decent depending on the origin city (NYC is just an example, I found these to be better ex-Canada)