HI Dave,
I saw a really interesting method recently that removes some of the tedium with measurement. The guy used masking tape, he stuck it across the stringers then used a pencil along the edges on it's side to pick up the "high spots" of the stringer corners, then transferred the tape to wood, and cut round the pencil profile. I'll try and remember where I saw it and post a link as he showed the method with some pictures....
Andrew