10-30-11: Jazdoc
Stringreen is also correct: the LPS is one heavy cartridge!
The 16g weight won't be an issue in the Phantom with the stock counterweight. I use a 15g cartridge and there is still plenty of adjustment.
That said, since the SLR has virtually the same motor as the LPS (but is almost 4g lighter without the body), there may be some sonic gains from having the counterweight closer to the pivot. This could be a contributing reason why some prefer the SLR(?).