the foils and the spks have the exact same flex rating, get it right.
the foil is exactly the same as last years 1080 boot.
the 1080 boot was made a little stiffer the last year it was made (from 75).
the cuff design of the spk gives it a more progressive flex than the 1080/foil. progressive does not mean softer, it means it doesn't feel like your shin is slammed into a brick.
the thick power strap gives support and disperses impact on your shin over a greater amount of suface area.
because of those last two points i probably wouldnt take off the spk strap, but if you ant to put a booster on put it above the stock power strap.
you are NOT standing straight up and down in the spk, it still does have forward lean.
your bindings automatically raise your heel higher than your toe, so you will have even more forward lean.
it is not a all mountain freeride boot, but its not like the foil is any better