I'm having difficultly trying to resolve this problem with stretchmax alignment. Here's some code to reproduce. No height can be specified.

Code:
Ext.onReady(function(){

      Ext.create('Ext.container.Viewport', {
         title: 'Parent',
         items: [
            {
               height: 300,
               width: 800,
               items: [
                  {
                     defaults: { flex: 1 },
                     layout: {
                        type: 'hbox',
                        align: 'stretchmax'
                     },
                     items: [
                        {
                           bodyPadding: 10, 
                           items: [
                              {
                                 bodyStyle: 'border-color: white; background-color: white; border-radius: 10px;',
                                 bodyPadding: 10,
                                 items: [
                                    {
                                       html: 'asdfa sdf'
                                    }
                                 ]
                              }
                           ]
                        },
                        {
                           bodyPadding: 10,
                           items: [
                              {
                                 bodyStyle: 'border-color: white; background-color: white; border-radius: 10px;',
                                 bodyPadding: 10,
                                 items: [
                                    {
                                       html: 'This panel will have more content than the one to the left. However, eventually the content from this panel is not properly calculated, and the content begins to disappear out of sight :( The expected result should be both panels should stretch to be as large as this one. I do realize that this could be a result of the body padding, equalling twenty pixels, pushing the content down. Perhaps align "stretchmax" doesn\'t factor in bodypadding?'
                                    }
                                 ]
                              }
                           ]
                        }                          
                     ]
                  }
               ]
            }
         ],
         renderTo: Ext.getBody()
      });
   });