When you are changing the trigger spring, remember the pin only goes in and out one way. Have patience with the spring itself... It can be frustrating without the USP trigger spring tool.
Talked to Bigbore and TooSixy and both said not to change either and I should like the outcome!Do NOT change the trigger rebound spring. At least not now. Don't change the hammer (main) spring either unless you want 9 pounds of trigger weight.
I'm not certain if the V1 trigger rebound spring is lighter or heavier than the Light LEM trigger spring but know for sure the flat section LEM spring is a beast.