I have a 110gr under my battery pack, which is about 240gr (Vampire 4400). For some tracks I made a thin weight to put between the battery halfs of about 50gr (75gr was incorrect
).
The extra 50gr are of course better for low grip, but add a lot of stability on high grip too, making the car less twitchy and easier to drive. So most of the time I use it on astroturf and carpet as well.
And for very low grip I had an extra 50gr behind the rear shocktower and removed 12gr up front, leaving 18gr (GHEA bulkhead) in total. I even added an additional 100gr under the battery, so a total of 240 + 100 + 100 + 50 + (50 behind tower) = 490gr, without lead behind tower. Which isn't that much, just 70gr above the Ni-MH weight.