The Jack Keller recipes recommend 6 to 8 lbs of muscadines per gallon of wine. His recipes tell you to add 3 qts water to each gallon wine. To me this means he assumes you'll get ~1 qt muscadine juice from 6-8 lbs of muscadines. Side note: If I cut the top off a 1 gal plastic milk jug and fill it with whole muscadines, it weighs about 6 lbs.
For my taste, the above is too "thin." I'd recommend at least 16 lbs of muscadines to make 1 gal wine. This means you'll roughly have a 50% juice and 50% sugar water (simple syrup) mix. Another side note: In order to get 2 qts of simple syrup, you don't put 2 qts water into the boiling pot and then add the sugar...if you do, you'll wind up with more than 2 qts syrup.
I use Montrachet yeast and back sweeten to ~0.998 SG. If you like it sweet, then you should go to higher SG...maybe 1.008h.
Bottled - Cherry/Lalvin 1118
Bottled - Cherry/Montrachet