I have the BH-40 on a Gitzo GT2540F, which in my view is the right head size for that tripod. On a Gitzo GT1551T I use a BH-30. I believe that would balance the GT1542T better, even though a BH-40 also fits. A BH-30 is more than capable of holding the weight you´re looking for and it is less weight (not by much though). Both heads are working very well and I recommend them both.
1DXII, 5DIV, 5DSR, 8-15/4L, 11-24/4L, 16-35/2.8L III, 24-70/28L II, 70-200/2.8L IS II, 100-400/4.5-5.6L IS II, 200-400/4L IS 1.4x, 17/3.5L TS-E, 24/4L TS-E, 35/1.4L II, 100/2.8L IS Macro, 300/2.8L IS II, 600/4L IS II, Zeiss: 15/2.8, 35/1.4, 55/1.4 Otus, 85/1.4 Otus, Profoto B1