Can I call a graphics object's method using the object's handle? (R2014B)

Hi all,

I was wondering if I can call a graphics objects method when I only have a handle to the object. Say for example, if I find a polygon in an image:

hPoly = findobj(gca(), 'tag', 'impoly');  % N.B. I'd love a more "robust" way than searching by tag

And I want to invoke the polygon objects createMask method:

BW = hPoly.createMask;  % not gonna work

I found the iptgetapi function but it doesn't provide the full set of methods. Currently I'm creating a new object and deleting the handle which is pretty ugly, e.g.

api = iptgetapi(hPoly);
verts = api.getPosition();
oPoly = impoly(gca(), verts);
delete(hPoly);

Thanks for any help