Kehut, I realize your question is answered, but wanted to say that a Michell Tecnoweight offered better tracking and a deeper bottom end over the stock counterweight in my system. It's a worthy upgrade you might want to research.
Rega Rb-250
Planar 2 with Rb-250. Have a Benz Micro ACE H on the way. Cart is 8.8g..do I need a heavy counterweight for the Rega?..I thought I remember reading the the 250 can take a cart up to 12g with the stock weight.