Really appreciate you quick response. You are right about the use of disc is needed because of the battery-less design, and it also maximize the compatibility with different iPad. The disc that we picked is very smooth, may be you will like it more after trying it. Some app have already supported SonarPen. If ok, you can try SonarPen on them. That save you the time to complied the SDK into ArtStudio.
Regards,
Elton