r - Integrating multiple shiny apps into one shiny website

How can one integrate multiple shiny apps into one shiny website?

I've tried using the navbar example and iframes, however the iframes sometimes have major problems with sizing and scrolling.

Here's the iframe code:

tabPanel("seam",
tags$iframe(src="/01_hello",frameborder=0,align="center",seamless=NA)),

note: seamless is basically not supported by most browsers.

It's also not possible to size the iframes correctly for each app, since the app dimensions change as they're used. I've even tried to use javascript to resize the iframe when needed as in here or here.

Any ideas?
I've considered integrating the apps as in the linked navbar example, however they're so different and use such large and separate datasets that it's unlikely to work well. Also using iframes allows separate threads for each application and makes things more manageable.

Here are some examples of failures:

1. Wrong dimensions:
   




2. For this one, if I shrink the height I get a double scroll bar, when I don't I get a large empty space.
   




3. Here's a double scrollbar.