Sorry to say this now, but I think you should have posted the initial question on LessWrong in addition to on your Facebook page. Getting 6 likes is impressive, but it was the only suggestion offered.
I hope you don't get too discouraged by all the dislikes. Hopefully they just mean that those people don't want that particular t-shirt.
Just to clarify, the initial question was posted on the Facebook Less Wrong group. But yeah, I guess I should have posted it on LW itself too, good point. Updating on that one :-)
Happy to share that, after multiple rounds of feedback, here is the set of rationality-themed T-shirts and bags with the slogan that got most support from the community, "The Difference Between Medicine and Poison is Dosage."
These t-shirts and bags are an effort to update based on the feedback received on the original set of rationality shirts and optimizing suggestions. This includes use of graphic images in the words, use of more professional designers, etc. We went back to the drawing board, and tried to design a new shirt that used a slogan that was quite popular. We ran the design by the Less Wrong FB group a couple of times (1, 2) and this is the final product.
As you can see, there are two styles available, one with "Dosage" empty and with the image of the dropper, and one with "Dosage" filled in and without the dropper. Various colors, sizes, and materials are available for each shirt/bag.
The first style is available for purchase on CafePress here.
The second style is available for purchase on CafePress here.
Look forward to hearing about your experience and thoughts about these t-shirts and bags, and the impact they make in carrying good rationality-themed memes into the world! We will be making more shirts and running them by the community as we did with these. All revenue will go into promoting rational thinking strategies to a broad audience.