Dale, Done that been there. I have 2 ROV's that with HB HDSI installed and Interphase Forward Looking sonar over CAT8 cable.
Total refit of each rov was US $6200.00 if you start from scratch or about US $3000.00 for the HB refit alone.
Bet the hell out of $30K to $60K the BIG ROV manufactures charge for a ROV mounted unit!
It was a DIY job. Thank You!
Roddy