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Yes the Italeri dragoon is a good choice. Three feet by two is not too small and will be a lot of work, especially the groundwork.
Ferguson was really a good officer. He led Washington go when he had the chance to kill him. And he introduced the first breach-loading musket.
A pity that the Americans got him and not Tarleton.
Good luck with the diorama
Don't forget the Imex Alamo Defenders set, which has a few figures in hunting shirts. The Davey Crocket figure had both arms raised making him best fodder for conversion, IMO.