I run Marys on a my tandems with HS33. Maguras fit and work very nicely on the bars.
What you notice is that you need a slightly longer stem (+10-20mm or so) with Marys or the front goes a bit light. Cromo ones are heavier and stronger but overkill for most usage.
Maguras are brilliant as fit and forget brakes - clip in some new pads every now and then and that's about it. The modulation is great - and they are powerful enough to stop a loaded touring tandem without fuss in torrential rain on a 1:4 Devon hill. Personally I think that discs are a bit more fiddly to get to run smoothly if you always swap the wheel out, but I'm sure others may disagree.
Ride it or milk it!