...the best way to do this is not to add bananas to the primary, but to slice 2 1/2 lbs of ripe (soft but not brown) bananas into thin discs for each gallon of fruit wine you intend to make, leaving skins on fruit. Put the slices into a nylon straining bag, tie the top closed, and place the bag in as much water as you need for your fruit wine in as large a pan or pot as required. For example, if you were making three gallons of wine that required 3 quarts of water per gallon, you would need a total of 9 quarts of water and 7 ½ lbs of bananas. You'll need a large pot, but could get away with using only half the amount her and adding the other half later. Just keep track of what you are doing.
Bring the water to a boil, reduce the heat, and simmer the bananas for 30 minutes. A grayish scum or foam will probably form on top and should be spooned away and discarded. Remove the bag to a bowl to catch the drippings.
While the bananas are simmering, chop or crush the fruit for your wine and place it in your primary with the required amount of sugar, acid blend, tannin, and yeast nutrient. Combine the drippings with the boiled banana water and pour the water over the fruit, sugar and additives. Stir this well to dissolve the sugar. If you only boiled half the required amount of water, add the other half now, cover the primary and allow the must to cool to room temperature before adding the required amount of potassium metabisulfite (or crushed and dissolved Campden tablets) to prevent the must from browning slightly during fermentation. Wait 10-12 hours and add the required amount of pectic enzyme. Wait an additional 10-12 hours and pitch an activated yeast starter.
