Unfortunately ntdllx3 is a dud. I tried to boot up with it and I got 0x6B BSoD with parameters 0xC00007B, 0x3, 0x0 and 0x0.
Or I meant it was a dud, since I decided to take it, change SectionAlignment back to 00001000 from 00000200 and it works just as well as x2. And it wasn't in vain since it's still slightly smaller than BWC's last ntdll.