Super_Duty...
Your original question actually addressed two things..... weight AND balance.
You're right, pure weight will help benchrest performance (some of the BR guys at my range are shooting HEAVY rifles) but at a cost.
The post by "Danish" is right as well.... My HP Service rifle weighs in at about 12.5 lbs and the positive aspects are most noticable shooting offhand.
The main reason that people use butt stock weight is, as mentioned, to balance against the weight of the heavier barrel configuration and the free float tube under the handguards. Balance is a personal preference. For me, and my positions, I've found I like it balanced at the delta ring. Though heavy, it is balanced, and "pivots" well the way I hold it during offhand.
A little tip: Stick on wheel weights work great. I use them to line the handguards and they haven't come loose. Start with just the lower handguard, and if you feel you need more, you can add them to the upper handguard as well. I also have them stuffed in the butt stock. They're cheap, no shipping of a "custom molded" piece of lead, and you can get them at any good auto parts store. See if they'll sell you a half box to start.
You're right, it's the practice and experimentation that gets to be the fun part. Good luck. Let us know how it turns out.