OK, I even broke out my powder scale so I would have exact arrow weights.
My bow scale isn't the best but I have checked it to find it's 3lbs light and I change the weights it gives to reflect that.
The only thing I changed on the bow between all the arrows was I had to raise the rest to make up for the thinner carbons.
Phantom II Straight limb, Nitrous-B cam, shoot through, 29" draw, 14 strand 452x cables, 20 strand 452x string, string leeches, Shurz-a-peep, string loop.
282fps with 362gr arrows @ 66lbs. 63.94ft/lbs .4533 slug feet/sec
250fps with 477gr arrows @ 66lbs. 66.21ft/lbs .5295 slug feet/sec
243fps with 507gr arrows @ 66lbs. 66.49ft/lbs .5470 slug feet/sec
Although I gained more speed with the light arrows than I predicted I still lost KE and Momentum. Although my heavy arrows were lighter than I thought I still gained KE and momentum.
I even took the highest speed the light arrows read and threw out the higher reading I got today for the 477gr arrows and took the average for the heavy arrow.
It wasn't perceiveably louder with the light arrows but the hand shock was more.