On your 'measured distance' is it on flat land? Or down hill.
Have thrown over 500 feet down hill, it is really easy. At Ellison, in New York.
Beautiful hilly course. With a beat up cheetah (remember them).
But come to Florida in the heat and humidity... good luck reaching what you say.
Now a Rhyno 800 feet sounds more realistic.
i can throw a pro wraith, star destroyer, and champ boss over 400ft now. i've increased my d by about 25-50 ft this year so far. try a pro wraith man. they start nice and stable and they'll beat in to a hyzer flip disc and then a nice roller disc as well.
I dont throw a power grip but, i do have a mean snap, thus creating spin. I can throw a boss consistently 450 with a wraith 500 and a groove 500. One drive i threw my boss 171 and maxed out on a hole of about 550 or more it was sweet.
However the most practical way is to experiment with different speeds of discs until you find one that works for you. Generally if you can't spin a disc up to its intended speed you will get less flight out of it (like when a first time player insists on throwing a heavy overstable disc). Slower throwers may be able to get more distance out of a midrange than they can out of a max distance driver simply because they can exploit the true flight path of the disc.
Adding onto that theory is the idea that weight plays a big part. A light disc is easier to spin up to speed and get some distance out of, but is more susceptible to wind.
In general the best way to get nice distance into a headwind is a heavy, overstable disc that you know well.
With a tailwind it's a light disc with plenty of glide.
Either way you will need a lot of practice. The key is not getting frustrated when you don't get things immediately. Muscle memory takes time to build up as does getting a good mental game going. Envision the exact flight path you will be taking, for every shot. Get yourself a confidence mantra. The game really is 80% mental which is why I get schooled by the middle aged guys at my course constantly. :)