But putting it first means going out of chronological order...and that means doing a temporal reversal early in the book to get back to the "real" beginning, which is still not as flash-bang....and all backward steps in temporal sequence feel slower to readers, which added to the slower pace in that section (necessarily slower and chock full of plot points that will blossom later on) will make it seem even slower than if it comes first, I think. Besides, I think keeping the chronology in order makes it easier for readers.
So, at the weekly fencing class (which ended up with no one fencing tonight), I presented this problem to alpha reader (m) and some others, and during the discussion, the youngest member came up with the best solution, which I hadn't thought of AT ALL. Since the beginning of this book overlaps the end of Oath of Gold (Paks III for those who have it in the omnibus edition), he suggested reprising a chronologically "correct" exciting scene from there, and someone else had said "Use a different POV" and the two ideas coalesced in my head on the drive home. While continuing to braid downstream, I'll be trying to write a new opening to the first chapter.