I have to say Dan & E are spot on.
After running the S2 last year which was very light with lipos in. I ran my X6 light for months with just a Trish bits front bulkhead as ballast & was more than happy with how the car was going, but over the lasts couple of months after speaking to E
I have been adding weight to the car at every meeting and found the car just gets easier to drive fast the heavier it gets
the funny thing is after weighing it the other day its at 1742!