Ha ha, Keith!
You keep staying one or two steps ahead of me! First, I saw that you had mentioned the book that I recommended in your first post. Then, as I was thinking about yr dilemma while walking my dog, it occurred to me that you could replace the 7th's drum with a French one and jotted down the two sizes of the drums as a reminder for when I got home, since I am getting older and more forgetful by the year. It occurred to me that you could have a generic blue and gold drum with a huge sabre gash in the front to show the bright brass, and then I remembered that you live in France and your house might accidentally get burned down. But you were ahead of me on both counts! However, I can give you the dimensions of the "French" watering bucket of the period, which was used by the British, so your house should be safe, from Franklin's British Napoleonic Field Artillery, pp. 61-2 and 64 The "French" version was 10" tall made of 10 3 x 1/2" staves bound together by three iron hoops. The bottom diameter was 10 1/4" and a little wider than the top, so your fusilier is unlikely to knock it over with his weight. You may well own or have access to this book, but I am having trouble with my scanner, so if you are stuck, I'll photograph the page and Email it to you. It would include a pic of the "British: version, but Hamilton doesn't give the dimensions for that. This is about 6" shorter than the drum, of course, but as God, you can always put it on a small hillock ("monticule"?).
Cheers. Phil