Personally, for what you want the 505T to do you probably shouldn't of gone with the pin up drilling, because that is the only way I can see the 505T being weaker than a Gravity Shift or a Tropical Heat Hybrid. Even with the pin up drilling it should only be weaker than the Gravity Shift. As far as the backend, if you are going 500 w/polish you are basically defeating the purpose of polish. The ball should at least be at 1000 before you put polish on the ball.
If you don't mind plugged balls I'd plug the ball and re-drill it. You could always try and plug the weight hole first, because putting it on the PAP was probably a bad idea. From now on when you buy a ball make sure that you throw it first before the pro shop operator attempts to make the ball legal so they actually know where to put the weight hole.
Also, when you are altering the surface are you actually running through the factory progressions? or going straight to the intended pad? Personally, I have my best experience when running the ball through this progressoin: 500, 1000, 2000, 4000, 4000 (with the six sided sanding method).