Below is a screenshot of the app. As can be seen at the bottom of the screen, above the navigation bar, is a small grey-ish bar that is cutting off the contents of the current tab. I scrolled my CustomListView so it can be seen that one panel is cut off.
If feel confident it's not the combination of layouts. The activity loads in a layout that just has one Tabhost on it. I've used the script section to set the tabhost width and height to 100%x and 100%y respectively. Inside the tab shown below another layout is loaded. All that layout has on it is a CustomListView, and that's been fully anchored to both sides and the top and bottom. So all views are set to use the full height. When I've used CustomListViews on other layouts and they're not in tabhosts they fully reach the bottom.
That's why I think it's not bad design and more how the tabhost is constructed on the screen, with a small 'footer' that in terms of colour matches the header that holds the tabs.