First off... go straight to Williams for the peep. They have one listed in their catalog as the Whitetail, that is the one you want. You can get it online.
You need to check out
http://www.dwbs.proboards28.com/ and learn a litttle more about what is happening with whites. Bullets are all over the place for your gun. The trouble with White slugs is that they are .503.
If your gun is even a little over bore, your bullets won't give you the best for the money. Bullets of .504 or .505 even are better and there are lots out there for you. There is even a gas check bullet that might be just the ticket for you too.
As for trajectory... sighting in High is not going to ruin your chance of best accuracy. If anything, compared to hold over, it will improve it. You need to try it out to see.
Aloha...
