I would take about 10-12 of them, at first (2 1/2 - 3 gallons, total - peaches and all)... Put them in a larger vessel without adding any water... Add 1/8 tsp of sulfites, give it a while/good stir and take a SG reading..
I would say use "most of them" - ie save enough to do a f-pack later, but if the light syrup has too much sugar for the alcohol level you desire you'll be stuck adding water and i would try to avoid that if possible..
If in fact the SG is too high in the syrup, and you did crack "most of them" open, you'd be making more than 3 gallons (adding water to dilute) or straining out peaches and pouring some syrup down the drain (to hit the 3 gallon mark).. Not a bad option, but opening a few and taking a reading will atleast give you a heads-up on how much work you're in for.. Either way if the SG is too high (dont think it will be, but not 100%) you'll have to add some water..
There is a chance however that your syrup isnt too high in sugar, in which case i would probably go with 'about 30', or 3/4 of what you have total, and save that other '10' or 1/4-total, for a f-pack towards the end of the process
I added water to my batch of peach wine - it turned out fine, but im wishing i hadnt, just for the simple fact that i know it would have been a better final product in the end, without the water..
Hope i didnt confuse ya, cause i confused myself for a second writing it out
