I used sycamore for 2 peices of my shop frame as a test. The frame is now 10 years old.Both peices were cut from the same log,boxed heart, cut to 12'- 6x8 with a 2" 45 degree rip along the length.supported by an outside wall they have performed just fine. Sycamore grows tall in the river bottoms, blows and twists in the wind witch causes ring shake.the bigger the tree the more shake. The best use for sycamore is cutting boards as it will not absorb food odor, it's what they use at the fish market.clean the fish ,slice your onions, wash it off and slice the bread,bread dosn't taste like fish or onions.
Tom