Hey Sha Do, have yo uever considered dumping those PDI springs (shiite) and tried out the First Factory/Laylax springs? Very consistant, and easy to pull the bolt back. I had a PDI 300% spring in my M24 for a bit, at first it was like cocking a cross bow, had to put the bolt on my foot, shoulder on the stock, and heavy assed trigger pull. I swear it was over 600fps though. I cut coils off, dropped it to a bit over 500fps, still rather heavy to pull but wasn't too bad, then after a few hundred shots the cylinder rammed my hop up unit hard enough that the screw that holds the hop up unit in place sheared out of the receiver and rammed my hop up and barrel a good inch forward.
Point being, those Laylax springs are the cat's meow, very good performers and easy on the arm (and trigger, and gun, etc.) The 150SP tends to put out close to 500fps, the 170 would be a good one for you, maybe even the 190 for certain fields.