Where did you get the stencil? Just so I know not to go there. I had a similar situation happen on a Chevelle SS hood years ago. Now, if I use a stencil, I go to my local trim supplier, he has the equipment, give them a drawing of what I need with dimensions and have them cut cut it for me. Usually while I wait. It doesn't cost that much and the situation you have is eliminated.
For the last SS striping I did, I laid the stripes out by hand, it takes a little longer but the results are better, I can fix my corners or edges as I go and make sure all is well before I paint. It seems I need to fix stencils in one place or another most times anyway.