Spring Selection-Assistance Needed

Hi all! I would be eternally grateful for some feedback and help on this. I am somewhat undecided on what spring I need for my gun. I am currently running an upgraded MB03 VSR-10. Not much of the original is left though.

The upgrades are:
Action Army 6.03 430mm Inner Barrel
Action Army Hopup Chamber
Maple Leaf 70 Degree Decepticon Bucking
Action Army Teflon Cylinder
Action Army Spring Guide
Action Army Receiver
Action Army Bull Barrel

The reason behind upgrading the receiver and outer barrel is because the originals on mine stripped out. As in, the threads that connect them stripped out entirely on both ends. So they were being held together by just that little tiny screw that connects them.(I felt as though I ought to explain why I upgraded those before other things.) However, upgrading the receiver and outer barrel allowed me to use all Action Army parts for upgrading, instead of dabbling in Airsoft Pro, as the gun started out as an MB03.

The reason for all of that information being given? I am about to upgrade the trigger to the Action Army zero trigger so that I can do a spring upgrade. I've been using the stock MB03 spring and trigger unit up until now.

All of that to lead up to the primary question: Based off of the specs I have given above, what spring do you recommend I run? I would like to run around 525 FPS if possible. The bb weight I intend to use is .43g. I can run higher or lower if needed however.

NOTE. I do NOT have access to a chronograph. That is why I am asking and why I gave all of the information that I did. With as many people running Action Army upgrades as there are, I figure someone probably knows about what I need. Thank you in advance!
BohemianLizardKing