Finally got to try out my OS32's. Have to say I love em to bits, did some pretty hardcore and brutal trails up in the Pyrenees and they held solid. The hook-on extra bags are a great feature too.

Just got a set of the new, slim OS22s for an upcoming Morocco trip.
Will be using them on a home made C-rack as regular throwovers (ie: without the platform).
They weigh 2.5kg each + straps and feel very durable.
The 32s would probably suit more people on a long trip.
Big enough to get everything in there with nothing on the back of the seat.
But the Lomos on the front add 6 litres each so nearly the same.

Fits nicely Chris. Plenty of support at the back edge from the rack so they shouldn't flap about too much.
You do like your Montana as an HUD don't you!