ATF FREE Pistol Registration - Form 1 or Trust?

If you use the ATF's FREE Pistol/SBR registration can you do it with a Trust or does it have to be a Form 1?

You can only do it on a trust if you can prove that the braced pistol, for which you're filing the Form 1, was owned by the trust prior to the publication of the final rule. Otherwise it's individual, and you can later transfer it to the trust on a Form 4.