Gray water Holding Tank Too Small

We own a 2004 2720 with a 35 gallon holding tank and a 45 gallon freshwater tank. We do a lot of dry camping. The problem we always run into is our gray water fills before we run out of water. Considered a portable tank, but it takes up too much room. Has anyone upgraded to a 50 gallon tank? Seems to be plenty of room under there.

If I put too much money in my wallet, it won't close. I hate when that happens.

I have 40 gallons of fresh water. I think the holding tank is 32 gallons. Apparently we drink or cook with 8 gallons of water because it never overflows.

We do cheat a bit. We use the water from cooking spaghetti to put the campfire out if we had spaghetti that night.

I run out of fresh water before I run out of holding tank capacity. I do not understand why I have different results, though I will admit that we do not have identical capacities.