I was cruising on a slight downhill road at around 15 mph in ECO mode 3 then switched to sport mode 5. It does not take much effort to hit that speed, probably within 10 seconds.
If you want to be stealthy go with the matt black with no decals, you won't be disappointed. They don't list options for the bike so just ask for them. Also, those aren't extra derailleurs you want, extra hangers for the derailleurs.
Buy a good shock pump and use this video for instructions. Once you get everything dialed in you will appreciate how the bike handles and rides.
https://www.youtube.com/watch?v=xhnKTZu2AKs
You are correct, 181 cm is 5'11". I'm 5'9" and the medium works great for me. If the medium was any larger it would be too big for me.
Maybe another AM1000 owner will chime in on this post for you.
I would go with the 52v batteries, its worth the extra cost. I don't think FREY will have any problems upgrading your order, I went through the same thing making battery decisions.
I have that same throttle on my AM1000 and it works great, better than the one that comes on the bike. It also moves the controller button closer to the hand grip which makes it easier to get your thumb on it.
Have you tried unplugging your throttle and two brake cutoffs then test riding your...