Custom region (for use in tpl file)

I would like to create a layout in omega which requires that my RHS sidebar is full height, allowing omega to manage the main content area (a common layout request from designs I am supplied at present). An example layout for what I am after is attached to this post

Initially I created the sidebar region in my .info file, but then noticed the region was classed as #excluded in the $page variable. To resolve this I have inserted the below line into my tpl:
$page['sidebar'] = $page['#excluded']['sidebar'];

This appears to have resolved the issue, although has also cause an error to appear:

Warning: Illegal offset type in isset or empty in alpha_theme_container->regions() (line 224 of /var/www/retrobadger.net/public/sites/all/themes/omega/alpha/includes/base.inc).

Now, whilst this is only a warning, I assume that it appears because what I am trying to do is not really what Omega is for. Is there a better solution to what I am after, or shall I just ignore/patch the error message to achieve the required result.

Thanks,
Dan

n.b
I was on 7.x.3.0 but have now upgraded the module to 7.x.3.1