Can't speak to the 55 MPG, but as for the 125 indicated, if he's running the stock tire size on the front, actual speed would be lower.
I've had my bike in the one-teens, and backed off when a nasty shimmy commenced. As sroby noted that he was 'skeeeaarreeddd', I'm guessing he wasn't liking the feel of the bike at that speed.
SISF has been in the one-thirties on his bike recently, and due to the front and rear end suspension mods, he was pleasantly surprised that the bike was riding smoothly...