Hi Ian

I am looking at the PrFive2 and think I would need a 54

I currently ride a Giant Trinity Advanced Pro in size M ... according to the stack/reach chart it says 539 vs 540 and 417 vs 425 for the Giant compared to the QR so these are pretty close.

I am 6 ft. tall and my trinity is set up with a pad y of 685 and a pad x of 395 to the rear of the pad. The tip of the ISM saddle is 90 behind the BB. The extensions are 360 from the back of the pad to the tip and they are flat (not much option to tilt on the stock trinity). The saddle to pad drop is 90.

The QR site indicates that based on my height I should be 54 or 56 so I am hoping to get a more definitive answer before I decide.

thanks