Not sure you want to move to 4 1/2 inches on the shock race sag. Several years ago, I started using Daryl at Acme to tune suspension, and have learned a great deal. Here is the process I have used for years:
- set your static sag at one inch (this is the difference between on a stand with no weight on the back tire, and off the stand with the bike weight only.
- Gear up and check the race sag. If you are 3 3/4 to 4 inches, the spring is about right for your weight/riding position. Much more, you need a heavier spring. Much less, you need a lighter spring. This is a general rule only. I have used this process when setting suspension for others, and have found some folks have had to set their static sag to 2 inches to get close to 4 inches. On the flip side, I have found static at 1/2 inch to get to 4 inches. Swap springs, and they ride much better, and with more confidence.
- A little more or less on the static sag can make a big difference. I actually run 1 1/8 static sag and have for years. However, race sag is still just under 4 inches, but I ride way forward on the bike, so my riding position unweights the rear just a bit.
Like most folks on this site at about 210 lbs, I have swapped to a 5.4 rear, and run heavier springs in the front (although I only run .43 springs. For most folks, the heavier springs are going to be the ticket).
If you think about it, by lowering your race sag in the rear, you are giving up some of the effective travel, which may result in more bottoming of the rear shock. Something you might want to consider in your tuning process.
Good luck
Rick