Here's the manual link (it has the extended battery detail)
http://www.bafang-systems.com/fileadmin/Media/Components/Motor/Product_Motor/MAX_Drive_System_dealer_Manual_EN_15-04-22.compressed.pdf
I've done about 800km on the bike already. I weigh about 80-85 kg probably and carry a load. I find that to go at 25kmph I usually need to go to a higher assistance level (or ride downhill). Any information about battery upgrades is very helfpul. I also have some experience with electronics and Arduino and would like to power up a flash light with the intended wire, maybe even a brake light, however that would require possibly having a connector between the e-brake's electric signal and another wire to switch the brake light on.
About speed settings - a rev is a rev, but the wheel sizes aren't great, I haven't tried to change size, however I thought 27.5er wheels with fat tyres also happen to be 700mm (700C). The tyre on the greenway is about 4cm each way, if the inner rim is 622 then the total diameter is 702 approx. Most 27.5er's seem to have the same end diameter, and are probably safer. The manual says how to align the magnet properly.
I would get a larger battery and run fatter tyres - lose some efficiency and add safetly, after all it is a heavy bike and could be nasty to fall off.
More to the point ... Is the bike water proof ?
The company informed me that it could be ridded in light rain but the bafang manual says to not completely submerge the max drive. I am guessing the circuits are treated like the one in this video
however the motor cannot be shorted - If they have not bothered then its a good upgrade for the case of getting caught in wet weather. I have taped over inlets and used celethane bags over electrical components (some standard lights will fail in heavy rain)
It's a good bike, although not without electricity.