A mistake on my little doodle has been pointed out by a few comrades here, so I went ahead and checked some of my measurements.
I was unable to unpin the sear, and the depth of the hole for spring is only a guestimate. The spring itself looks like it could be fashioned from a mechanical ballpoint pen, but the actual length and stiffness are unknown for the above mentioned reasons.
If you have any more Politically Correct questions, I will do my best to answer them in accordance with Policy of Standards and Norms.