I can't remember the last time I've weighed my buggy, but generally most drivers in my area tend to prefer larger capacity packs which increase weight to help add stability and increase length of run time. The club in my area does 10 min mains, and there are folks who struggle to make that length as their packs age.

Only time I have heard of weight being an issue was when Ryan Lutz lost his podium position in nitro truck for a national race, it was just a few grams too... basically lost weight from tire wear... the lesson learned there was to not get anywhere close to min weight IIRC.