how many leafs should I remove?

[hpcgmc]

I'm trying to "undo" the rear leaf springs on my truck so I can see how much I want to lower it. My plan was to unbolt the leafs from the hanger, then lower the frame on a floor jack and see what the truck will look like with 3,4 and 5" drop, then I can decide what to buy. I plan to put it all back together so I can drive the truck while saving up cash to buy the lowering parts.

Here's my problem - I jacked up the frame, with the wheels on the ground. I removed the hanger nut. When I try to remove the hanger bolts, they are pretty tight and seem to be under pressure. Using the floor jack, I've tried to adjust the frame height to where I think it is not supporting the weight of the axle. I'm a little nervous about just pounding the hanger botls out with a flat headed punch, for fear that I'll have a big "bang" from the spring pressure.

Any suggestions on safest or easiest way to do this? This is on my 67 GMC half ton with stock suspension.

EDIT: I jacked up the fram a bit more and it removed the pressure off the springs and allowed the hanger bolts to come out without any "bang". Dropping the leafs all the way to the bed only seemed to lower the truck about 1.5", so it doesn't look like lowering hangers will make much of a difference. I might remove 3 or 4 of the leafs and see how much difference that makes. I've got 8 or 9 leafs on there now!