You have a good point, however, I doubt too many people compete with that large of an oven, so they may be a little more forthcoming with recipes and tips. You also might ask on Yahoo's Dutch oven cooking group, IMO they tend to be a little more open about sharing recipes. Also, in the Yahoo group's files there is a recipe converter that's an Excel spreadsheet. I've never tried using it, and it only converts up to a 20-quart oven, but you might be able to play around with it and use it to calculate the quantities you'd need for your oven (I think the 22" holds 45 quarts).
Joan Larsen's cookbook, Lovin' Dutch Ovens, has a couple of recipes for a 17" oven. One of them, which is a stew, notes you would double the recipe for a 22". If it would help, I could send you that recipe.
About the only other thing I know about MACA ovens is that they're thicker walled, so they take longer to heat through than other cast iron ovens.
I wish I could be of more help, but the largest oven I use is a 14". Good luck!