Good tip, if you have one, is to have a full-length mirror when kitting-up, just to check things are in the correct positions.
Fixing the belt to abdomen at front, either with chicago screws or snaps help to keep the belt in position. It needs to be on the kidney part, not the butt plate, which is probably throwing other bits off line.
And yeh, the shoulder bells should be pretty much touching the shoulder straps. Are all the arm parts connected with elastic?