Hi: Meckwell does play support doubles to the four level. I also play them. but up to the three level(3H inclusive) and only with shape/values to hopefully protect partner. The exception at the two level is unsuitable hands. Those that have lost value Qx etc. due to being in the suit that the other pair has bid reduces your hand to minimum/subminimum. 4333 shapes need more than minimum values. I would guess about a 90/95% support double rate at the two level. We also make support doubles at the three level, however, the shape/values tend to show more than a minimum hand. Regards, Robert