Yes it takes less pressure in 2.5's due to increase in surface area of piston

Example:

2.0 piston surface area is 3.14sq-in multiplied by 200psi=628.3185 lbs of force

OR

2.5 area is 4.9sq-in multiplied by 128 psi= 628.3185 lbs of force

So less air pressure but applied over bigger area is the same force

Later

Crashed