Whether you keep any bass really depends on your forage base. If it is healthy and producing lots more fish and forage numbers seem to be abundant then SPM is correct, don't keep any of the original bass. But knowing if the forage base is adequate or even optimum is a key and important part of the 'equation'.
Since you are fairly new here and if you are truly intent on growing big, great bass, as I know the management, to determine if the bass have enough food,,,, take length and weight measurements of each bass you catch. Record the data. Then check to see if they are mathematically plump.
Do this with the Rw formula where it says to take the bass weight and divide it by the standard weight of the same length of bass. Rw (relative weight) is also called Wr. (I always convert everything to ounces for my calculations; remember that 0.8 lbs is 12.8 oz not 8oz). Then multiply the answer by 100 or in ewest's example below use % (.92). Fat well fed bass have Rw value of 85+, better is 90+, and 100+ is very, very good - fatty bass. When the value for that fish drops below 85 or 80 toward 70 that bass is not getting enough to eat- meaning forage items are in short supply and or there are too many bass compared to numbers of forage. Note that female bass during spawning will always appear fat, but the plumpness is egg mass not true body mass i.e. 'fat'. Spawned out females will appear thin bodied and have a low Rw. Be aware of when you are taking your Rw samples compared to spawning season.
All this is similar to monitoring the BMI (body mass index) of yourself or family members to determine their plumpness. But for healthy family members you want a lower value, however for your bass you want them tubby to even obese with a high Rw value.
Please come back periodically and update us as to how your F1 bass are growing and their plumpness as determined by Rw (Wr) values. Pictures of your F1 bass are always nice for members to see.
There are various tables of numbers here on the forum that give you the standard weight of LMbass. I found some information of standard weight of LMbass.
From Aquatic Environmental Services - Greg Grimes
http://lakework.com/wp-content/uploads/2013/01/Largemouth-Bass-Relative-Weight-Index.pdfFrom Bass Resource
http://www.bassresource.com/fish_biology/growing_larger_bass.html Thanks to ewest: