What emboldens me to make the try is that they might not lead hearts, which will let partner pitch his, even if he has trump loser. I hope in assessing his trump quality, North envisages a void rather than a small doubleton. No worries there, Jim. That's what made 5S my second choice, just behind Pass and just ahead of 5H, which really does give EW information they may need to set you. I'm not all that comfortable with passing, just less comfortable with anything else.
Any bid here is risky.
If yes, then bid on. If no, pass. And be ready for the postmortem. The reward is, after all, a vulnerable game at IMPs, something to be sought for vigorously. All I have for sure is the ace.