I ride a 57 Lemond Zurich and a custom frame with 55.5 Seat Tube and 57.8 Top Tube lengths. I'm looking at buying a Pinarello CX for 50/50 off-road / on-road riding. I've read through a lot of CX sizing comments on this and other forums, but am still having a hard time figuring out whether to get

54 Seat Tube
55.5 Top Tube

or

56 Seat Tube
56.5 Top Tube

Based on previous comments, should I be shooting for my 57.8 Top Tube length and go with the second frame that has a longer Seat Tube length?? Or will this put me too high for a CX bike??

Thanks in advance!!