The biggest issue for FOC Vortex is the tail, too small and short. And when transform into the bruticus, the tail just doesn't fit.
I found using ROTF Blazemaster tail, I can easily fix that issue.
1)
as shown in the picture below, cut the pole in the left yellow circle, then modify the right yellow circle part a little to make it fit. Then just screw them together.
2) I repainted the tail, the blade and the weapons together. Since I don't have a fit red color, so I just painted them all black.
Almost no impact to the original part, except in helicopter mode, the combine slot need to be down all the time.
3) And it sure looks better in hand mode
4) This is the robot mode, looks better too.
from side
back view