I'm going to be casting something in smooth-on flexfoam-it IV. It has an 80a to 100b mixing ratio. So 5:4. I need to have a total of 700g of pourible material. I'm sure it's something obvious but I can't figure out how many grams of each I need to pour. If I just try to top off the difference like doing the 80% of 350g first then I will end up with having to do 120% of the other part to reach 700g again. This doesn't seem right... than you for any help.