It looks like the last design I posted has won out as a favourite, so to make things less stressful, I'm just going to go with majority rules.
And it seems like people are okay with the Paypal option, and paying once for the shirt, then a second time for the shipping.
I did look into USPS flat rate shipping (thanks Lakelady!). I'm trying to figure out if it would be a good workaround for the shipping cost. I have one of the small boxes and I think you might be able to fit one shirt in it (making the shipping cost $4.95). It's when you get up to the bigger boxes that it starts to get pricey. Click here to see details. What do you think... too pricey?
I'll update as soon as I know more!