Set textblock position on Canvas based on center origin

Hi all,

I'm having a issue where I'm trying to position a text block on a canvas but its position values are based on the top left coordinates. I've tried using the render transform origin and setting the point to 0.5,0.5 by its not letting me set the position relative to the center of the text block. I would like to set the X,Y from the center of the text block not the top left. Any ideas?