Just when I thought my build was progressing smoothly I got blindsided by spider poop. I was ready to put the deck on my Mill Creek 13. I had stored all the parts properly (I thought). The two deck sections were lying on cardboard on top of one another with another piece of cardboard covering them. Spiders hibernate during the winter apparently finding the space between the two deck pieces a cozy place. While they were snoozing they also pooped on my decks (and yes I know what spider poop looks like). The poop was black and soaked into the wood leaving several black spots that I can’t seem to be able to remove by sanding. The deck will be bright so this is a concern. I don’t know what it will end up looking like after fiberglass and varnish but it was an unpleasant surprise. Maybe taping around the edges would have eliminated this problem but they could have entered between the cardboard and wood too.
Can you reverse the parts? I don’t know the mill creek but on most of the kayaks you can reverse/flip parts and get the other side to show….have used that technique on occassion…but only works if you like the other side or other panels that also have to be reversed…
Reminds me of my first build back in 1976. It was a group effort with a bunch of us building 14 Sabot look-alikes. We were mystified by the little yellow spots that kept appearing on the fresh paint. Finally, it was discovered that the neighbor had bee hives and as the little bugs left to go pollen hunting each morning, they would empty their bowels when they got far enough away from the hive - which was exactly over where our boats were drying.
My sympathy.
Laszlo
I tried flipping the panels but the best match for the wood grain was on the sides I wanted to use of course. I looked at it this morning and the sanding got most of it, my OCD self was on full blast when I discovered it yesterday. Sleeping on it helped. When the new site starts up I think they should change the name of the Builders Forum to OCD Anonymous lol.
Condensation from the AC ducts dripped water onto curing epoxy on several pieces of my boat. It not only ruined the epoxy coat, but stained the wood beyond repair. Another reason I chose to finish with paint.
This boat was built with boards that had cat urine stains all over them. Came out ok….and looked nice from a couple paces back. Each boat has a story 
The boards were given to me for free after the owner (the one with the cats) gave up in frustration. Worst parts were flipped to the outside and the nicer, more interesting stains, were used on the inside.
People thought I had done something ‘artistic’
I can just imagine what sanding over cat urine smelled like but the boat looks amazing
I have found using oxalic acid (available on the Amazon website) to be effective in removing some forms of discoloration with no harm to the wood. Try dabbing a little bit on a small area with a cotton swab first to see if it works. Good luck.