I am in the process of my own experiment in my new fruity at home.
it's a £25 jackpot and seems to repeat quite regularly, so i have noted the cash in & out meters since the last jackpot and will see how much it actually takes before it gives another.
it's set at 78%, and i will try various methods whilst playing, like purposly gambling the cash prizes untill it loses or hits jackpot.
will keep you all informed.
machine is called "Reel Thunder"
if anyone wants me to try any other methods, just let me know.