Since receiving the woven pine Fastrider pannier last summer, I have been using it as my main transportation bag. On the up side, it is enormous, waterproof, classic looking, easy to attach and detach, and secure. On the downside, it was designed for appropriately enormous Dutch bikes with long chainstays, and not for bicycles with road geometry. The pannier looks like it's ready to swallow the mixte whole, and ideally I would like something smaller. But for a bicycle with short chainstays finding the right pannier can be tricky.
Royal H. mixte was not designed as a transportation bicycle. It was designed for light touring (not too much luggage), and it was designed to be ridden upright in hilly areas. The chainstays are 430mm, which is somewhere in between classic road and classic touring geometry and appropriate for what this bike was meant for. So in theory, all is as it should be. However, in practice I've been riding it for transportation more than I had anticipated - just because it's such a fun bike, and the dynamo lighting is so excellent.
OYB Swiss Army pannier is a perfect fit for the constructeur rack, and it goes nowhere near my heels when I pedal. Alas, it is about 1/2" too narrow to fit my laptop. I've tried stretching it, but it's just not sufficient, so I use it as a camera bag. I also tried (and returned) the Linus single Office pannier. While it did fit my laptop, the attachment system was difficult to use and did not feel secure: leather straps with snap closures.
It seems that the trick to designing panniers for bicycles with short chainstays, is to make the pannier vertical rather than horizontal, to mount the hooks lower on the bag (so that the bag itself will sit higher), and to keep the size as small as possible. But while some touring panniers are designed in this manner, I have not been able to find a suitable one for commuting - by which I mean a single pannier that attaches and detaches easily via strong and secure hooks, is large enough to fit a laptop, and looks classic, ideally made of canvas or leather in a grayish/greenish/brownish colour scheme. If you are an artisan who would like to give this a go, get in touch! And if you commute on a bicycle with short chainstays, what is your pannier solution?