Galvanic Isolator Installation

[redcobra]

Since I have rewired my boat and added a VERY expensive Maxprop, I have decided to add a galvanic isolator. The wiring diagrams shows the GI in the green wire circuit between the shore power and the AC double pole breaker. On my boat, the SP goes to a terminal block way up in a narrow space (then to the breaker) and the Green ground wire terminal then has another green wire that goes to the boats DC neg buss. The space where the term block is very hard to get to and no place to maount the GI. However the green grounding wire that goes to the boats DC Neg buss is an easy reach.
Is there any reason the GI cannot be installed between(inserted) in the AC ground wire and the Boats DC neg buss connection? Single 30A SP circuit.
Seems the principal is to isolate the AC ground from the DC Neg buss with the GI.

And, there are $98 GI's (Yandina), $198 GI's (Guest and Newmar) and $398 GI's (ProSafe One). All 30A versions.
Will one work as well as the other?