Here's an update with LONG overdue pictures!
I don't know the weight of the new piston, as it was pre-installed in the jug and I didn't get a chance. But, judging that the wrist pin alone was 25% lighter, I'm betting the piston will be similar. It shakes a whole lot less up top now!
EDIT: After browsing Hammer's website ( www.hammerperf.com ), it looks like their piston weighs about 304g. Compare that to 433g for the stock piston - again, a weight saving of over 25%!
Stock piston & wrist pin are about 540 grams together. Hammer's piston and wrist pin are 380 grams. 540g divided by 380g gives ~1.42 - showing that the hammer stuff is over 40% lighter than stock. This is why you can rev the motors higher, and not have them come apart!