[neallewis]

For me, on rubber gym floor low traction tracks I use +12g on rear bulkhead and it really helps with traction and grip. certainly doesn't make the car "worse". I already have 25g under motor, no front weight, and 25g plate in cut out under lipo. I found adding much more weight to the car "worse" on low to medium traction, so front and larger underlipo weights. loosing these, and weight placement as I described works best for me.
Now on medium/high grip astro I loose the +12g rear weight, its "worse" in this situation. I also use either +11g front bulkhead insert weight, or swap to the steel. I've also used the plate in front of servo, but generally prefer it without.

More serious weight changes also require damper oil and spring adjustments. overloading a car with weight and not making the right adjustments could it "worse"

Its all subjective, and changes are track appropriate. Team setups may have worked on that day at that track, but may not be right for you on the day at your track. test the options and weight placements yourself at your local track, and judge what makes an improvement, or makes it "worse".