i purchased my 1st (BSA) red dot sight for a 2400KT i ordered. after mounting it on another rifle to check the sight picture, i noticed that the dot changes position depending on how i rest my cheek on the stock. (i didn't sight it in) does the dot have to be in the center of the sight picture to be on target? also, i was surprised to read the factory setting for parallax is 50yrds. i thought with a 1X sight it would be set much closer.