I haven’t tried drying Manchester. The tree I have has only produced a few plums previously, but this year it’s pretty well laden, so maybe I’ll give it a shot. They’re great plums, and freestone too. My experience with American, Asian, and hybrid plums is that drying concentrates the tartness of the peel, even if slight, to an unpalatable level. Pretty sure that’s the reason domesticas are used for prunes, since the skins are sweet.
The same situation obtains when making old school apple jelly or shelf stable apple butter, which have no added sugar, relying on juice alone for sweetness. Unless low acid, very bland “sweeting” apples are used, the final product is pretty brash. I’ve found a few sweeting apples that are hardy here, and am propagating those while searching for more. Altaiski Sweet is a winner, and Alma Sweet and Renown. Last year a seedling tree I planted more than 20 years ago bore for the first time, and also seems promising; looking forward to evaluating it again this year. Clair 16 and Wodarz are other candidates, which are full sized apples, unlike the rest.