VSR10 PDI Spring Ratings

[Fabzster]

Hi

I have a TM VSR10 upgraded with the full Edgi Upgrade kit

430mm 6.01 TB
7mm Spring Guide
Custom Sears
Custom Piston
Custom Cylinder Head
Laylax Teflon Cylinder

I am Looking for a spring that will keep me at 500fps.

I see I can get a Laylay 150 but I cant get one of those so what would be the equivelent in the PDI?
I have also seen MAG springs but have no idea what they like or how the rating works

also being that I have a 7mm spring guide what Diameter spring do i use? (only 7mm?)

Please assist