Yep, Sigelei #20 was actually my first mech...I actually gouged the insulator pretty badly trying to get the switch apart. Honestly, I think on the older versions of the mod, the switch was meant to be taken apart (seen it done in YouTube videos), but not on the newer ones...I tried for a long time to get that switch apart to no avail (looks like the same version as yours).
In addition to what crxess said, Mark Todd from toddsreviews.com got his #20 firing better by replacing the spring with a stiffer one (pretty sure it was a stiffer one)...the review is still on his site anyway, for reference.