Do the following
- Drive under speed limit without annoying too many folks (50-55mph)
- Dont use the A/C if possible, use low fan speeds
- Reduce display brightness to minimum (does anyone know if we can put it into cleaning mode when moving, that might be best)
- Use Range mode
- Dont load up the car with any additional weight if possible
- Try to not punch through with the accelerator as tempting as it may be with the torque
- Use regen braking effectively, notice changes up front in advance and use regen gently to slow down at a lower rate first and then release to use max regen to come to a near halt
IMO you should be able to do the distance without too much difficulty with the above.
Also are you certain that there are NO charging stations whatsoever, need not be a supercharger, there will be other slower third party charging options available, even if it takes much longer its a back up plan work working into your route just in case.