1) If I am performing sujood on a flat surface for example on a limestone floor then is it permissible to just place ones whole forehead and nose on the limestone floor where the whole middle area and a part of the right and left side of the forehead are resting flat on the limestone?

2) Ruling 1031. Based on obligatory precaution, [for the purposes of sajdah] the ‘forehead’ refers to its middle area, i.e. the rectangular area when two imaginary lines are drawn between the place where the eyebrows begin(1) in the middle of the forehead up to the point where the hair grows.

If I am understanding this correctly the required area is around 1 inch in width in the middle of the forehead. If I am prostrating on a turbah and theturbah happens to be placed slightly to the left or the right on the ground so that when I prostate on the turba I find that half the turba is touching the required middle region of the forehead and the other half of the turba falls outside of this region i.e. it slightly to the right or left, Is the sujood valid?

1. Yes, it is permissible
2. Yes, it is valid