Thanks for all the help guys.
I made some 12" plum open-pour worms last night with 1 tablespoon of flotation additive per cup of plastic. It really whitens the color so i had to use a lot more colorant and also offset with black. The color is still different because the entire worm becomes so opaque. I tested the worms on a jig in the hot tub, and while they do not go vertical, they do stand about 35 to 40 degrees off of vertical. I sent several packages to friends today to get some feedback so we shall see.
If someone knows where to buy a darker colored float additive, please let me know. Thanks