8S 4000mah will fit.
just need to do some cutting.
4S 4000mah x2 in series
Battery Compartment Modification
Battery Compartment Extention
8S 4000mah, Perfect Fit. Batteries WAY UP FRONT for CG to balance an HET 700 motor
you might not need to push your batteries that far forward since the Lander DPS fan should be much lighter.
the HET 700 series are heavy.
i have been considering swapping out to a Lander DPS.
but i have yet to try them out.
the Lander DPS units look good though.