Add custom jointjs shape to rappid stencil pane

I'm trying to build a prototype by using some of the examples in the Rappid tutorial pack - namely QAD and KitchenSink.

From QAD, I have a custom element defined as:

joint.dia.Element.define('qad.Question'

From the KitchenSink, I have stencil groups defined but the elements in the groups are json objects, eg:

App.config.stencil.shapes.standard = [
    {
        type: 'standard.Rectangle',
        size: { width: 5, height: 3 },
        attrs: {

I've tried to take the relevant parts of the definition of qad.Question and add them to the stencil group; using the identifier from type as a string; using joint.shapes.qad.Question and setting it as a variable and using that, but each results in errors.

I think I may be missing something obvious - how can I add this custom shape?

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