If you get the infrared taxi cam version of the A129 then it comes with a short cable ideal for mounting the rear camera on the front windscreen or mirror housing.
You do get a better rear image if you mount it on the roll bars, visibility from the mirror area can be quite poor with the roof up, but it depends on what you are using it for, if not for movie making then using the taxi cam version may be a good option.
You could also consider a bike cam, since they are waterproof, but even Viofo's MT1 bike cam doesn't have all the parking mode features of the A129 Duo, similar image quality though.