Like I said, I really don't think it's a matter of the heartline roll's length. They're only replacing three pieces, so it's very unlikely that it'll be lengthened. The problem is that it's not perfectly heartlined, especially vertically... Watch a video of Colossus at TP and compare the perfect heartline rolls to Maverick's current one, and you'll see how poorly done the original trackwork for Maverick is in that section. Maverick's track is barely heartlined vertically, so it probably causes a sudden uncomfortable g-spike.
I'd bet money that the new track pieces are primarily to heighten the middle of the roll so that the heartline works perfectly from now on.