I have the stock ballast on my 2004 Mobius LSV. Does anyone know when filled, how heavy the single sack in the ski locker is? Also, I have looked at adding manual filled sacks in the storage areas alongside the engine where the additional sacks for the 3-sack ballast system would go. I have seen a package for two 350 lb sacks from Straightline - does anyone know if the dealer/factory option is the 350 lb sacks or do they use larger??