Is there somewhere locally you could dry the boat
out? A gravel beach or similar? That's the easiest way to get to the keel
on a boat of that size. Similarly, your trick should be fine if you don't overdo it. An alternative is to moor somewhere and take a line extending the main halyard
on to the dock
and walking away from the boat.
But the answer to your question is that the mast
are easily strong enough to take the forces required to heel your boat right over as far as you like, as long as you don't wrap it around something on the way.