I think it's going to be small for you. The reach is not that long as the FM326. Have you tried it already or still waiting for delivery?
I understand your concern, but based on the geometry I think size S (52) fits me better.
The jump to size M (54) adds around 20,5mm of stack, which is quite significant. I’m currently riding a LightCarbon LCR018-D in size 52 with only 5mm of spacers and it fits me well.
My saddle height is 69cm, so I don’t need the extra stack. Also, the top tube on size M is noticeably longer, which would make the position too stretched for my preference.
With a 100mm stem, the S keeps the position more balanced and avoids being too stretched or too high in the front.
So for my setup, S makes more sense.