Oxford Aqua T50 or T30 roll bag

[Cwodavids]

I want to buy one for commuting to work with a few days worth of clothes and a laptop but the T50 look far too big for an FZ6 and the T30 seems a bit on the small side for the amount of kit I want to carry.

Does anyone have either of them and have an opinion on pros/cons?

I am guessing the 50 and 30 litres are maximum sizes, can they be made smaller if required?

How easy do they attach?

Anyone had bad experiences with them?

Are they a danger when at or slightly ? Above the speed limit?

Any help greatly appreciated.

Dave