Shawn- The letter from Whittle, Jr. to Minor's location is mentioned in a previous post on this topic.

For more insight into what these people were thinking regarding gunboats please see Whittle, Sr.'s thoughts included in testimony regarding the fall of New Orleans.
Questioning of Captain Whittle by the Confederate Senate regarding events preceding the fall of New Orleans, Series II, Volume I, Pages 445-446, ORN.

That success in the Gulf would have been fleeting or not would have depended on ability to maintain and build reliable strength in the form of more shipping, both in vessels and crews. That conditions did not appear to likely to change for the better was motivation for the crews to seek out potentially viable alternatives. The vessels abuilding in England seemed the most viable, both to this crew and to Federal Minister Adams, who threatened England on the basis of their existence.