Play testing is not only fun, it is VERY good at finding issues with the rules. I updated the optional wounds section to make it clear what happens when all wound slots are full and the character receives a new wound. I thought I had it covered, but when play testing Mythiria (a fantasy game based on Flexpiel), a player pointed to the wound rules and said my ruling didn't align with the rules. After some discussion, I figured out why. The rules in the document were very ambiguous. 

I fixed that. Here's the updated section:

Characters have 3 wound slots. Describe the wound and write it in an empty wound slot. If all 3 wound slots are full, a new minor wound causes an existing minor wound to become severe. A new severe wound causes 2 existing minor wounds to become severe.

Thanks for the catch Neil!