Blanket stitched circles

I am attempting a flower on a piece I'm doing but I don't have step by step instructions. Basically it's a blanket stitched circle with bullion loops around the edge. It makes a pretty attractive flower. I'm doing this on 32ct linen and want the circle to be about 8 threads deep (radius). I've taken it out twice now as it looks too square-ish. Any rule of thumb for doing a circle in this manner? I've tried stitching every thread (too dense) and then every two threads (better) with a reduction in depth from the centre at the corners (trying to make it round). Hope this makes sense to someone. Was hoping someone may have done this and knew a method for circles. Any and all ideas welcome. Jeanine in Canada (who is curve-challenged when it comes to needlework!!)