GeorgeC1,
Agree if arrival to EIS is 11:40... (And being late by 45 minutes would not be unusual). Getting thru customs may be time consuming, so helpful to "walk fast", be at front (Although number on planes tends to be fairly small).

Unless pushing arrival up, I would agree 4pm would better target for most. (I have been off the dock in much less time, however I as owner, do not need boat briefing (agree 1 hour should be allotted for this, simultaneous with separate group getting off the boat and provisioning, which also helps with boat briefing). Also, less experienced will likely take more time with each task(inventory, purchasing provisions, stowing provisions, etc).

Practice speeds up the process, so your 2020 goal should be to charter more often to improve efficiency ;-)