Well, it took off. And it flew. We also recovered it.
Despite the woefully inadequate launch platform, it cleared the rod without issue.
The issue appeared when the rocket weathercocked hard as the motor burnt out.
The chute didn't deploy until just before it hit.
The rocket was recovered with pretty minor damage. Just two broken fins and a little dirt on it.
In hindsight, the 3.1 cal reported for stability in open rocket should have been a red flag. My thinking was that any extra stability would help with the lack of power. This may have been acceptable with a dead calm day, but the 7mph or so winds proved to be too much. After a few adjustments I see no reason why we shouldn't see a successful flight on an F15-6 (although 4 would be a much better choice...).