I'm in progress of choosing a new bike (or more specifically trading my MTB for a CX), and have asked for a CX with stack and reach numbers fitting my current road bike, an BMC GF01 'endurance' bike (I ride it with the stem low with only a conical spacer under it, and I'm very comfortable on it, even on full day rides).
size 51: tt 527mm, reach 365mm, stack 546mm, st angle 73.5
However it turns out that the reach of 365mm for a '51' frame is pretty 'short' in today's geometry standards.
Is my thinking valid, prioritising reach to match, and sacrifice height on the stack? Or should I keep looking for a close-to-fit on both numbers?
Of course a lower stack means I can get lower and as a result more stretched (not that I want to), but too low means an awful lot of spacers which is a no-no.
For reference some example numbers.
BMC CX size 48: tt 518mm, reach 368mm, stack 506mm (reach ok, but stack is 40mm! lower)
BMC CX size 51: tt 534mm, reach 377mm, stack 530mm (reach is over 10mm! longer)
BMC RM size 51: tt 539mm, reach 376mm, stack 550mm (-"-)
Cannondale Super X size 48: tt 505mm, reach: 365mm, stack: 515mm (reach ok, but stack is low)
Giant XTC size S: tt 530mm, reach 370mm, stack 540mm (reach is 5mm longer)
Focus Mares size 51: tt 534mm, reach 365mm, stack 537mm (close to my GF01 geo)