MrB: I am not keen on switching out my pair of T18's either. I run both primarily on 2,6Ah batteries and think it is a brilliant drill for size balance, weight and run time with the 2,6Ah batt's. The new clip does add something that has been missing all along though.
Judging by the looks of the new clip it looks reasonably strong considering the backside will be supported with a battery in place so it does not look too fragile to me. I will be happy to try it out.
I had plans of making a belt clip hack but haven't gotten around to it so I will be happy to try and retrofit one of the bonafide belt clips. I have a DRC 18/4 as well but hardly use it after getting a T18. The DRC works fine with the 2,6Ah battery of course but it is a heavier machine to boot.