With teh hammer approach using inertial weight you will not have NEAR the cutter power as a levered (bolt cutter style) cutter. There are bascially only 2 methods to improve the cutting power of a hammer.
Increase the speed of the hammer ( larger air intake at the cylinder(more, faster flow) and a LARGE OPEN exhaust port area)
Increase the weight of the hammer ( not always the better choice )
Just make sure you keep your pinky away from that area.
(;-) TP