i use a ribbon and a dynamic(i know ribbons are technically dynamics blah blah), or a ribbon and a condensor, or a dynamic and a condenser. placement and mic choice are contingent on song, room, artist, genre, whim, time of year, position of the planets, what you're wearing, and most importantly: how it sounds. move the mic around until it sounds the way you want. you dont have to use both mics in the mix. you dont have to put 100 mics in front of the cab. its fun to find the right spot. i've found that putting the mic right up on the cone usually sounds strange and disembodied to me, so i'm usually back at least 1' or more.
i'm not a pro.
slipperman is a pro. listen to him. his records sound great.