Flybobby
The Island Class cutters used by the US Coastguard are essentially the same as the UK Customs cutter Sentinel (although they have much better engines - but that's another story......). They were built under license from Vosper-Thorneycroft. VT's customer liaison people are legendary for being helpful to boat modellers, so you might start there with your research. Sounds like Tug Man is also on the case, so good luck.
FLJ