Well.. if we are talking B class boats designed for the rules.. Manta, Tornadoes and Quest B2s were all designed for the rules. Probably a few more designs but Im not familiar with...
Mantas looked like a T but had a anti-pitchpole rail at the bows (which could do the reverse once the rail went under!!) Quest B2 had a glass bottom and ply sides..
My club had 10ish Mantas, a couple of Quests B2 and 8? Ts .. Then the Ts took over..

There were a few Cs but the Ds were few and far between.. The Ds were mainly in the States if I recall correctly..