I'll snag a Valve Body from work & go through the mod with you, Just keep in mind it will shift into 1st at ANY speed!!
Higher Rate PR Springs boost pressure in a Linear fashion, The increase at full throttle/high load is fine, It's the increase at Idle/No load is the issue in a street vehicle with a sub 3000 stall converter as it will bang into gear. If your going too run a High Stall Converter......You won't feel it.
Large Ratio Boost Valves boost pressure in a Progressive fashion, Good pressures a full throttle with No increase at Idle/no load conditions.
**The Sonnax 400-LB1 does include a 10% stronger PR Spring, This is the increase in pressure at "No-Load/Torque Signal" in the Graph)**
I added the Red Line to reflect about what the CK PR spring will do.