hmm - out of the many dozens of brno rifles I have scoped - I have had none that require Millet type windage adjustable.
Yes the 550 is the same as the 600 series (and ZG and 21/22 series) - they are all designated as 19 mm dovetail.
I have used Warne, Warne QD, CZ, BRNO, Leupold, ..... those Australian ones, one piece, 2 piece,... they all did not require any fiddling with windage.
But - anything is possible with a re-chamber. Perhaps - look at the Burris (if they still make the 19mm, and se if they have rings with the plastic shims. I find those to be more effective then the Millets.
I tend to prefer the 4 screw BRNO/CZ mounts myself. Although I use the warne non-detachable on my 602 30-378 and they work very well.