yes, you can switch back and forth with lipo's and ni-mh's. i have 2 sets of lipo's and 2 sets of ni-mh's for mine. the esc is set up for 70% cut-off, so just be sure that the lipo's have a full charge on them before you use them or else you could run the risk of draining them to low. here is a link to the esc's directions and the text about lvc from directions.

http://manuals.hobbico.com/gpm/gpmm1800-manual-v1_1.pdf

It’s IMPORTANT that the battery is fully charged before being
connected to the ESC. The ESC will automatically set the low
voltage cutoff point based on the voltage of the battery as
soon as it is connected, multiplied by 0.67. For example, if the
battery has only 50% full charge when connected, the ESC will
set a low voltage cutoff that is too low. So make sure the
battery is fully charged prior to every use.