Just to clear any possible confusion...
"Flemish" refers to the way the string is constructed. "Fast Flight" refers to a brand of string material, and is also used generically referring to HMPE or "High Performance" materials.
If you are referring to using it as a center serving, any of them will work, although you may need different sizes for a proper nock fit, as dacron strings usually run larger than "fast flight".
If you mean loop serving...depends. Halo, 62XS, and even nylon work for loop serving, but with Halo and 62XS you don't want to go with the larger sizes. 3D is a great end loop serving, cheaper than 62XS or Halo, and much more durable than nylon.