PMW-EX1 with 1.6x telephoto convertor

I do wildlife videography and the 14x lens on the EX1 just won't be enough reach for my purposes. I was wondering if anyone has used a 1.6x telephoto convertor on a similar camera for HDV recording and just how well do they work - as in picture quality?? Century claims theirs has very limited effect on light gathering ability, is this true?? The pound and a half on the end of the camera concerns me as well, should it?? Century's web site says they are in the process of coming out with add on lenses for the EX1.