Painted Bumblebee Stripe advice

I will be painting my 69 Swinger soon and would rather have a painted stripe than a decal due to longevity . I am using a single stage urethane and no clear coat . If I use a stencil I know I must paint the tail portion white then apply the stencil then paint the red body colr and remove the stencil.
How do I make the edge of the stripe blend into the body color without a ridge if Im not using clear ?
I painted the stripe on top of my single stage urethane and no clear coat. I'm happy with the way it turned out. :thumbsup:

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