I've never found it difficult to install the metering lever. I just sit the carb body on the bench with the metering chamber facing up. Drop the needle and spring in their respective holes, gently lower the lever straight down on the spring while engaging the needle with the slot on the arm. Hold in place with a finger and install the screw. No force required. Once in awhile one will be stubborn then I just hold the spring compressed a bit with the point of an X-acto knife or something similar while installing the arm. Maybe I just have better finger dexterity than some but I really don't believe that is the case. I have certainly worked with many tiny things over the years though eyesight is becoming a limiting factor as I age.