The old 30 gallon tank held about 8 gallons of water. The new 50 gallon size tank only holds about 15 gallons. That is just the way pressure tanks work. When working properly, about 75% of the tank is air and 25% water at best. So if you have the right air charge and the tank is good, you probably have about a 20 GPM pump.
When the pump fills a bladder tank that fast, many times the pressure switch and gauge will see 60 PSI and shut off the pump before the bladder has fully inflated. After the pump shuts off, the bladder finishes expanding and you see a slight drop on the pressure gauge.
An 80 gallon tank only holds about 25 gallons of water, which would make your pump run a little over a minute. But a minute of run time is the bare minimum for the pumps survival. 2 minutes of run time is better, but would take 2 of those 80 gallon tanks to do that. Running continuously while using water is the best thing for the pump. A Cycle Stop Valve would keep the pump running continuously as long as you are using water, then it would only allow the tank to refill at 1 GPM. So a 4.5 gallon size tank would really be all you need with a CSV. The 30 gallon or 50 gallon tank would also work fine with a CSV, and would be much more tank than is really needed.
So you could purchase an 80 gallon size pressure tank or two and slow the cycling down, or you can eliminate the cycling with a CSV1A and use whatever size tank you have. When the CSV is filling the tank at 1 GPM, the bladder has time to expand as needed and you won't see the pressure drop after the pump shuts off.