Ladies, I just made a sample, as Annis suggested. There was no problem attaching the trunk to the tree with the seams pressed inward.
However, there was a HUGE problem in attaching one block to the next one below it! I now believe the seams MUST BE PRESSED OUTWARD. Otherwise, when you sew together two trees one below the next in a vertical row as we're going to do, the inward-pressed seams of the trunk are right on top of the summit of the tree where there are seams from the tree tip AND the left and right background fabrics.
Way too much bulk there if the tree trunks are pressed inward!
Well that was my lesson-learned today. Good thing I asked! My instinct was sooooo OFF!
The lesson: when in doubt, try it out!