Anyone more far than 20m would be able to sneak around without any fear.
In range 15-19m (45f cca? really dunno) ... the sneaking character would have to pass Difficiulty 5 Stealth check.
In range 10-14m (30-44f cca) ... the sneaking character would have to pass Dif. 10 Stealth check.
In range 5-9m (15-29f cca) ... Dif. 15 Stealth check.
And finaly in 0-5m (0-14f) ... DIf. 20
That's too much granuality IMO - stealth is just a part of the exerience. Make each individual system too convoluted and the whole game become unmanagable.
Stealth checks shouldn't be passive - they should be done against enemy's perception.
