I did it 2 days before the LR patch, because I wanted to have 100% on everything before I update. Imagine my look when I realized everything went back to 0%... That combo is a nightmare. You can do the palm with 643P, I think.
Congrats! You're almost there! The way I do the instant double palm now is Half-Circle Back(63214), Forward(6) + P. Be sure that you hit that 4 though(Back), or it won't come out.
Ooops, looks like it's 463P, not 643P. I can do the move on its own 10 out of 10 times, but for some reason when I try to do it after the knee the game registers it as 214P.
No prob and I actually have to retract my statement...I just went to experiment with the 463P method and it seems to be the optimal method in completing the featherweight combo, so go with that.
I actually used this to get through it in Ultimate, but I stopped and opted for the 632146P(Which works to execute the move) method...I guess mainly because I'm a little more defensive and I get a bit more guard buffer time, but that's not helpful in completing this challenge...Overall though, KING JAIMY is right, use this one.