Hobbs poly down will give nice loft and appear fluffier than a batting like W&N. If that is what you usually use. Wool is also quite lofty but also very expensive. You should be able to quilt without a problem with the polydown but be forewarned that polyester battings are slipperier than cotton or cotton blends so make sure you baste well to avoid shifting. Also, even without stabilizer, T-shirt quilts are really heavy so expect a good work out doing this on your DM. You may wish to send this one out for LA. This place is really cheap and includes high loft poly batting in the price of LA
http://www.happycrafters.net/quilting-services.aspx