[Suicide Junkie]

I'll use your example.

With an option of one more Shield V, or two fixed SR Vs (same space) heres how to decide.

SR V x2 : 50 shields/turn
SG V x1 : 300 shields/battle
PSG V x1: 375 shields/battle

so 300/50 = 6 turns into the battle, you have regenerated more than the 300 shields. 375/50 = 7.5 turns

So, if your ship is going to survive more than 7 turns after first getting hit, replace some shields with Regenerators.

So, design with shields until your ship can take 8 turns of battle damage, then add regenerators instead.

(I use these things all the time - they work great, esp. against theh long-range, inefficient weapons like CSM & WMG)