Hi dgraviett,
As suggested earlier, I think it's an issue of the Arduino and changing it to a Ri would make your life a lot easier. However, having said that, you can simply get this result slightly improved by modifying your code a little.
I'm not sure if you can use your TFT is a similar way as others use MFCDs but that'll be certainly a good experiment. If you do try sketching by exporting CDU, please do let us know about the results.