Getting Extended Project Fields and Customizing them

I am extending the Project Field Controls (thanks to the PWA.WebParts.ExtendableProjectFieldPart class) and am able to add project fields to my web part.

So as to add my own controls depending on what is on the page,  I would like to know what Project fields are on the page.

If I create my custom controls OnLoad or in RenderContent, my controls aren't added to the DOM properly. They only work if I create them in PWA_OnPreRender but I can't get the other project fields (with foreach Control c in this.Controls) .

Is there a way to get the current web part controls in the PreRender function or is it too early in the page Life cycle?

Thank you.