T-Shirt Transfer Help

[Mufftastic]

I am building a muff clone and want to include graphics on the stomp box.  I've built many tube amps and a bunch of pedals (too many to count) but I''ve always been a sharpie kind of guy.

I want to use the t-shirt transfer method Kit Rae and others have used.  I'm using "light" transfers because my box is white.

My issue is that when I peel the transfer off of its backing paper, it's super flimsy.  When I try to heat set it using a hair drier (Kit Rae's method on his big muff page) the transfer doesn't stay on the box, it blows away under the airflow from the hair drier.

Is there some fundamental trick I'm missing?

Thanks!