How far can one safely deck a 225 block?

I've never seen anything BUT flat tops for the slant, so you're not gaining anything "there". I know from direct experience the head can stand over .150" because I've done it. As for the block, all I have is what others have said. Maybe @Charrlie_S will chime in and give some experienced figures on the block. The .100" figure given for the block wouldn't surprise me though.