The ratio I see kicked around the most is 60% Cab Sauv, 30% sangiovese, 10% Merlot (all =/- 5% or so).
I did an old school Super T with 60% Malvasia Nero and 40 % Sangiovese, from juice buckets. It turned out wonderful, made 5 cases in 2014, have 3 bottles left. Malvasia has been supplanted by...