Re: removing hull numbers
I found goof off with a reasonably fine "steel" wool equal worked really well after using a heat gun of some sort. I would also recommend one of the better plastic scrapers vs a steel scraper while removing the lettering with heat.
If it is not clear, find "steel" equals, not the real thing! That will generally speaking protect the hull best while still removing the material.
She drives me boat,
I drives me dinghy!