I've got a Bike Box Y-Frame trailer - the pre-cursor to the Carry Freedom one - with an aluminium (waterproof & lockable til I lost the key) instrument flight case which attaches onto the base with 2 bolts (now changed to wing-nuts for quicker removal.) I use panniers, bar-bag & rack bag for touring, but use the trailer with panniers on my hack bike for carrying all sorts of stuff, mainly video equipment, tripod etc for work (camera carefully padded into the bar-bag.) It's fantastically stable on the road & at speed (also ok on not too rough tracks), with only a slight 'tugging' experienced when I carried a large leisure battery. Instead of the aluminium box it's also easy to strap on a big rucsac or dry bag onto the base through the holes provided, & with the wheels popped off the thing folds flat to go into a shoulder bag for use on the train (I've been trying to email Carry Freedom to source smaller pop-off wheels - as found on the City trailer - to make this even easier, to no avail so far.) It's pretty flexible, & I've been really happy with it. Only 2 minor issues: the need for a stand on the bike as it's easy with a 2 wheel trailer on to forget the bike won't stand on its own; & don't jump the bike off kerbs at an angle or the trailer tips over! Best thing is that the alu box is plastered in reflective tape which seems to really freak out following motorists - on our fast, dangerous roads at night they always stop before they pass me - I think they don't know what the hell is in front of them. Bliss!