I am Boris Badurina from Croatia
I work in underwater construction and designing underwater tools, specialised equipment and machines
I agree with Ion discussion on rov hydrodynamic, but there is a little more to it.
rov need to be in hydrodynamic equilibrium but also in static equilibrium, or at least as near as possible.
proposed solution is on good way but drag caused by batteries is not included.
batteries will lover the center of head hydrodynamic resistance, which will cause torque moment because center of hydrodynamic resistance and center of thrust do not lay in same line.
this will induce forward pitch and it will increase with increased speed.
another thing is that in proposed solution center of mass is lower than center of propulsion which will also produce forward pitch, and it will increase with increased acceleration.
same consideration need to be checked for backward motion as well as up and down
this may or may not be important to someone.
Static equilibrium of the rov in this case is more important because it will have much bigger impact on rov behaviour. centers of gravity of motors and batteries are all on the back and center of buoyancy is forward which will result in wrong position of the rov.
this can be adjusted by pushing batteries forward.
it can be considered as simple balance (but underwater)
both issues have to be considered simultaneously and some compromises adopted in order to reach best possible solution.
I hope that Ion do not mind that I used his pictures.
I hope this will be useful to someone.