[Ryland]

6 T105 golf cart batteries weigh around 400 pounds and would give 150+ miles of range, I also already have those batteries.
The 20 amp hour 36v lithium battery is around 20 pounds and is a great size to have on the bike.
I agree that going with a higher voltage is a good idea because at 20mph the motor is seeing the same voltage no matter what the pack voltage is, but right now I have the 36v controller and I could use the money so I'm giving my neighbor a great price!

The motor it's self is designed to handle up to 72v and there are people using them with 96v controllers and a few who are using them with over 100v.
There is also someone on EV albums who has a side by side tandom recumbent with solar panels on top, that bike weighs 320 pounds and they said they have space for 100 pounds of cargo, so around 800 pounds total pushed around by the same hub motor.

Heat is what really kills motors and I plan to put a thermocouple inside the motor on the windings, because they are what is going to get hot first.

I really like the design of some of the cargo bikes, but one goal here is to be able to haul 8 foot and longer lumber and dirt, for stuff like that a trailer just seems more practical, move the weight away from the bike and keep it low to the ground.