"Can you get away with a little out of perfect spine by let's say 10# ?"It enables you to shoot a heavier spine arrow, not necessarily "more forgiving" all the way around.
In other words, if you had a shaft that was 10# lighter in deflection (spine) than you should have and you front loaded w/200 grains, you would be further from where you want to be, than say just putting 125 grains up front.
If you have stiff spine arrows per your bow weight, front load them until you have reduced the dynamic spine to match your bow weight.
Bare shaft tuning or paper tuning can help identify appropriate spine and hence, good arrow flight.
Hope this helps -
Kris