your wrong about the rear rotors warping, I believe the reason why we have a drum parking brake system and not a caliper parking brake system is for that reason, after racing your rotors and pads get really hot and if you yank the ebrake after you park the hot pads will grab the rotors and warp em. Well the drum pads are not super hot because your not using them so you can't warp the rotor, you'd warp the drums b4 you warp the rotors.

You can machine slotted rotors also, or was it drilled?...

Always torque your lugs too, invest in a good torque wrench you can get a fat torque wrench from pepboys for about 20 bux, easy to use set the ft/lbs to 80 and tighten that sucka till it snaps.