This is my intent - add five or ten a year. I put in 20 4"-5" on April 14th. Today the five I just caught are 9"-10" and feel fat. Is that acceptable growth in four months?
An inch a month would be acceptable growth rate for our southern area spring hatched Hybrid Striped Bass.
4 to 5 inch HSB in mid-April would likely be "carried over" fish but don't know hatchery methodology for your area.
You have healthy fish - don't know the size of your pond/lake but annual stocking rate about right - "it all depends" on your harvest plans.
As you know, HSB are an outstanding sport fish as well as excellent table fare.
Good luck on your program.
George