Replying to 270 on - slipping out

So this past month I've been trying 270 ons (My natural spin is to the left but I spin right in order to land on my natural grind). I've made a few but I slip out and land on my side for the majority of them, which ultimately leads to me trying them less.

Is there any special way I should throw them in order to balance myself correctly on the rail? Is it merely a matter of me keeping my legs farther apart? I noticed my head only turns about a 220-230 degree rotation instead of a full 270, could that prevent a full spin onto the rail?

Thanks in advance!