I read this thread last week and went to the slidelock website and ordered the 14". OMG, this thing is great! I fussy cut the March block for Jinny Beyer BOM and it never slipped once. I'm a leftie most of the time but use my right hand a lot too and the slidelock works fine either way. I'm also coordination-challenged and my ruler slips on almost every cut. Not anymore!
Highly recommend you purchase one of these.