Thanks for your advice, this is the response I got from him:
Replace the first stage spring only. If you don’t have something small like a dental pick in your gun tools, you can remove it by taking the cover plate off and lifting the 1st lever off of its axis pin. 2 BB’s will be liberate, so do it over a towel so that you don’t lose them. Push the 1st spring through the hole instead of pulling it out and replace the 1st lever over the pin. Replace the BB first in the 1st spring hole followed by the spring you want and the set screw. Last thing to do is replace the other BB over the 1st sear screw. Refer to the drawing for location. Replace the cover plate and you should be all set to adjust the pull weights to suit.