You don't need the Maritime dish or the $250/month subscription - just get the Standard Dish and use the Mobile Regional subscription for $150/mon. If you're too far from the coast of an island, you can toggle on/off Mobile Priority for $2/GB as needed.

On our Atlantic crossing we used a standard dish with Mobile Global subscription ($200/month) - unlimited data when within 12-20 miles of shore (France, Spain, Portugal, Canary Islands and St Martin). Offshore, we toggled on Mobile Priority as needed. I swapped the subscription back to Mobile Regional once we were in the BVI. And "Paused" the service once we were done cruising the BVI.

No need to mount it. I set it on the sky bridge seating area off to the side on some cushions or the floor from La Rochelle to Arrecife, where I MacGyver'd a fishing rod holder that worked well until TS Cindy. After the crossing and for the 3 weeks we cruised the BVI, I just left it up In the Sky Bridge.

There is a Facebook group called Starlink on Boats which has lots of great info.