There are several kinds of mulberries out there, most common are the red and white mulberries. The white one can have red berries just to make things confusing. We have both here in WV, the white ones with white berries are very sweet but no acid and very little flavor. Our red ones vary from little flavor to excellent balanced flavor, except the trees are freakin tall and a PIA to pick the high berries. So we planted some Illionois Everbearing mulberries and are pruning them to open centers making them much easier to pick. If your berries dont have a lot of flavor is it really worth trying to make a wine from them? Even if you use 100% juice you are just making a weak flavored watery wine. As for the skeeter part, we dont make this but I would assume the acid part of the pee would balance well with the low acid of the mulberries, and since people get flavor in their pee from just the gross lees of the previous wine almost any amount of berries would probably work, but if you want to get better mulberry flavor try to go over 3 pounds/gal, if you just want a rose pee less would probably work. WVMJ