Been there, done that, got the T-shirt

Current model has different sized upper and lower spars. I sorted out all my stock in neat rows and piles . . . and I still used two identical spars in my first panel instead of one wide & one narrower. Had to snap out all the ribs, repair and build again. Only ended up replacing one. Luckily CA is easier to snap vs. Titebond II. Part of why I don't quite trust it.

In the past I've installed bulkheads upside down. Trimmed spars to the wrong mark on the plans (at the edge of the sheeted section instead of the center). Dyed a canopy Easter egg purple when I was trying for dark gray. Dropped an 18" metal ruler through a just covered wing and had it bounce BACK UP THROUGH THE NEXT PANEL OVER! AAAARRRHH. My right eye is twitching again.

I usually walk away and apply Jim Beam to my tonsils and lick my wounds until the next day.