I don't know Bedouin - the pistons of the Thunderbird are bigger than those on the Rocket. Assuming most else is equal the 55 pound difference seems believable to me.
I was comparing the Thunderbird specs to a Harley Softail Heritage Classic which is 328 kilos while the standard Rocket is 319. I don't think 295 is too much to expect.
2007 America, Phantom Black/Sunset Red
Deposit down on 2010 Thunderbird - can't wait for it!