Hey Chevahh,
What size Madison are you riding? The Large Madison compares close in tt length to the 56cm Mark V, and the X-L Madison compares in tt length to the 59cm. The Main difference appears to be stand over height which is like 2cm higher on the Schwinn's.

http://www.schwinnbike.com/products/...ail.php?id=724

http://www.irofixedgear.com/index.as...WPROD&ProdID=6