Cyclocross - CX and SSCX races and training

I'm looking at cross bikes and the Vitus is pretty high up the list at its current full build price. I'm the same height as you but run a 74.5 mm saddle height. Guide puts me just outside of small and at the bottom of medium. Should I size down?
EDIT: ignore that just checked geometry geeks and a M energie evo is 3mm shorter with 8mm lower stack than my road bike so I'll go with that as a small will probably be too aggressive and I am getting old