Ok thanks, I think this makes a point on my next move with the combo system.
Thank you very much.
Anyway, playing a little bit with my implementation (one montage for each combo) I have found that if I have to switch between anim montages it works perfectly to use Montage_SetPosition. This gives me a great blend between the montages as they stop and start in a point where they have exactly the same pose for the skeleton. So now I have to decide if switching to the one-montage-per-attack implementation or not as it is working also in this way.
All the other blending problems comes from the fact that there are a couple of animations that ends in a pose very different from the Idle one.
Thanks again.