Tut tut RB! Company 737 manual says "For fuel efficiency, the bags should normally be loaded in the rear.".
For 'S-n-R' - I have never been skilled enough to notice discernable handling changes on the 737 with CG movement. Pax distribution is pretty crucial, and model specific, and you should fairly quickly be able to pick up a pattern of how/where to load pax and bags for each a/c. My basic guideline (7372/3/4/5/7) with equal A/B/C pax is 100 in 3/4 and rest in 2 (very small trim change in 2). I don't fly 8/9 but I believe the pax need to be biased forwards.
I have NEVER had to have any re-distribution in 20 years. Only problems have been when pax have been badly seated. I don't know how the 'free-seaters' cope!