Some colors of DF97 are larger diameter than others which causes a little difficulty (for me anyway) when twisting a flemish string. I understand that some dye colors cause more swelling of the fibers and that the problem exists with other string fiber brands as well. Would there be anything wrong with using 1 less strand of a larger color or 1 less strand of a smaller color to even the bundle size? Any other recommendations on how you deal with this?
The most trouble I've had is usually with white being smaller (in all materials). You can drop a strand with the larger, or add a strand with the smaller, but it may not fix the problem completely (may add/remove too much).
Right after you start your second loop, constantly check to be sure you have even tension on both bundles. If you see one bundle getting some slack in it, cheat it out by adding a little extra twist to that bundle as you go (don't try to get it all out at once).
Chad
If I find that problem, I add an extra strand of padding in the bundle with the smaller diameter.