I pasted this:
But if you ever want to use a charger to keep you phone or GPS charged on tour, you'll get better performance at low speeds with the SON28.
from:
https://www.peterwhitecycles.com/schmidt.php
There are lots of ways to turn dynohub power into power for GPS, etc. When touring, I run my dynohub power into a Sinewave Revolution to produce USB power. There are several other competitors to the Sinewave too. My particular Garmin does not play well with a Sinewave directly without a pass through cache battery in the circuit. So, I send my dynohub power to the Sinewave, then the USB power from the sinewave goes into my pass through cache battery. And then I draw power from that battery to feed into my GPS to charge it. I can charge my GPS while I am rolling and my GPS functions while being charged. I think the B&M werk includes a pass through cache battery, and I think the Forumslader (spell?) also includes a battery, but the Sinewave does not.
The 105 is 130mm. I did not know if your frame was 130 or 135mm, often touring frames are designed at 135mm because touring bikes often use mountain bike drivetrains for lower gearing. I suspected that the 520 might be 135mm for that reason, but if you know it is 130mm, you are set. It used to be that 130mm was considered a road size and 135mm was a mountain bike size.
With a steel frame, you can put a wheel in the frame that is 5 or 6mm off without a problem, other than the wheel does not drop right in. I am using a 135mm hub in my rando bike frame that is 130mm. And I am running a 126mm hub in my vintage road bike with a 120mm frame. Thus, it is not that big of a consideration, other than the wheel dropping right it without having to work at it if you have the right size.
The last half of my five week bike tour last summer, I was self sufficient on power from my dynohub. I wrote up a description of what I use and why on a different forum. Some of my electronic device choices are a bit esoteric, so I am not saying it is the right way, just what works well for me. The link to that write up is at this link:
Electrics that I use for bike touring - what works for me.