Python add-in, GPToolDialog and Feature Set

Hi,

I have a script tool that has a feature set (interactive user input, e.g. draw a freehand polygon) as one of its parameters and works OK when run from ArcToolBox.

I plan to share this tool conveniently as a python add-in, so I tried invoking this GP tool using pythonaddins.GPToolDialog on an add-in button, but it seems that didn't work because, while the tool dialog appears on click, the dialog is modal in nature which prevents me from switching to the map frame to draw? Is this a limitation of pythonaddins.GPToolDialog?

Cheers,

JJ