If the letter size doesn't suit you (larger than most other companies send), you could get the $20 sample that is 24"x24". On 4 sq. ft. it's pretty easy to tell if you'll like it or not. Just make sure to put something dark behind the sample, as an AT screen over something white looks terrible.
Also, we offer 30 return guarantee on everything but cut DIY material orders. The most you'd be out is shipping, but again the 24x24 is even lower risk.
Finally, the upgrade policy enables you to upsize later in case you feel that you want more later on.