If you want to add some battery capacity later, you might try and build your own Lipo bottle battery.
If you haven't seen his bikes, Nader's ebikes are inspiring.
your suggestions during the build were great help, so thanks.
I stumbled across the link you provided for Nader's bikes few weeks ago, that's what got me started.
his bikes are exactly what I was trying to accomplish. love his simplicity & elegant bikes.
thought about a water battery bottle, but than I won't have a place for my water bottle...
BTW, RTR weight is 21kg. OK I think for a full suspension E-mtb.