He did it to at least one Martin too. CFM & Co. were mightily impressed - included a feature on it in 'Sounding Board', so I'm led to believe!

BTW, he's an artist. I don't think it matters to him what quality of guitar he's painting on. There are a number of extremely fine Old Masters in The National Gallery, London which are painted on, amongst other things than canvas, wooden boards - no less a piece of exceptional art for that.