I have a GT4330LS which is really on the safe side for my SL66. I would recommend a 3 series Systematic, though a 2 series would suffice (used a 2 series carbon fibre borrowed from a friend once and pictures were sharp). If you donīt need carbon fibre the GT3330LS may fit you well. Have also a look on the G2270m head, its buttery smooth and the best 3-way head Iīve seen so far.