During last week I spent some time thinking about these spells, and considering the following:
Staying cannot be applied to strike, you can apply a pressure but lacks momentum to make the same damage as a strike, but using Spell Mastery the spell can be applied in certain areas, making possible to use it as an attack spell (for humanoids or any other species the spell caster knows well).
These effects allows an RR by the target.
Pressure
Staying I 1 lb Mild dizziness
Staying II 5 lb Pressure on the jugular, after CO/15 rounds passes out, after 8 min dies
Staying III 25 lb Pressure on the carotid, after CO/10 rounds passes out, after 5 min dies
Staying IV 50 lb Pressure on the trachea/larinx, after CO/5 rounds passes out, after 3 min dies
Staying V 100 lb Pressure on the chest, target cannot engage in anything streneous
Staying VI 200 lb Completely paralyzed and heavy pain unless a Hard ST roll
Staying True250 lb (10xlvl) Pressure can liquefie a bone