Leave 1/8" even at the miters. Tsk, tsk, tsk...That's half your problem right there. If you left the gap, you'd be that much further away from noticing.
If you are worrying about 1/16" on a deck, you could be in the wrong business. After a month of wood moving around, 1/16 is not going to be noticeable. Tight miters are nice, but they are real, real tough to keep looking good long term.
The color difference is obvious. My guess is that your distributor is sending out some older stock. I run miles of XLM and never had the color issue.
I've used the Kreg Jig on short run mitres and haven't had anything but happy HO's. I keep monitoring my work to see if things change over the course of time, haven't had any huge issues yet. I'm in a good test climate, our temps range from -40 to 104F... If things go south, I'll be the first to admit my procedures need tweaking. In my experience, you may want to think about gapping long runs, that TT XLM loves to expand and contract... I'm sure some of our other professionals have had experience in this, hope they'll care to share as well! As for the color, has TT given you any feedback?
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