If your straight has a sling plate in the middle of the stock you don't have a "field stock"
That is the straight tactical version.
Your only real option assuming that is the stock you have is a grind to fit recoil pad.
Good luck
Mill a ball end mill groove along the top left side of the gas block where it interferes with the FFT and it will turn into place no problem.
If I get time I will post a pic.