WOW - that is fantastic! I was able to get it working as well by including the underscore (I read elsewhere not to when referencing a page).
I also had to create a default.html.twig file under "templates/modular" with the following:
TWIG
{{ content }}
</div>
It is now working exactly as I hoped, thanks for all your help and please give me a heads-up if I should to tweak the contents of the above default.html.twig file.