By the way, here is the canondale chart.. oops, link didn't work, well just click geometry from their website listing.

From 52 to 50 the top tube length only decreases 1.2cm, easily an amount correctable by stem length BUT, the number that matters, reach, only decreases by 6mm. So you add 6mm more to the saddle post setback and 6mm more to the stem and you're in the same position with same reach.

However, the standover height only gets 2 cm better.

You can go all the way down to a 48 and the reach only gets 1.2 cm shorter. Still easily correctable with a longer stem. That would get you 3.5 cm of standover clearance which sounds better to me. It's starting to get into altered trail at those sizes and I guess might handle slightly differently.

tl;dr: With very minor adjustments to seat and stem you can get the fit to the same length even in two sizes smaller. With another brand you might also find shorter bikes in the same reach.