And I can relate to the redesigning aspect. I'm doing that with the RX-79 (G), aka the Ground Combat Gundam used in the series the "08th MS team". I have my design in my gallery, I call it he Gundam Abram.
I agree on stiff but I think its the design in general. I suggest reducing the shoulder armor or widening his legs (a bit domish) and fix both head and chest and you are golden. (remember, he is for high mobility and low armor)