Heavier contra/torque spring..... lighter or heavier rollers

I just put in a heavier contra (drive) spring because the old one was failing. My 6.5g rollers that I was using isn't a good match. I only have 5.5g DrPully sliders and 7.0g, 7.5g roller weights I can put in it.

Should I go with 5.5g? I would think I need heavier roller weights to make up for the stiffer spring. Am I right or do I need to go heavier?

 

so I went from 6.5 to 7.5 with the 1500 spring............ lost 5 MPH top end. Maybe the roller weights still aren't heavy enough, got a weird harmonic vibe now too.