G'day, mclaughlin, and welcome to
Kunena.
Our general advice - without addressing the specific problems or issues that you have raised - is to use the latest version of
Kunena. In this case we recommend that you upgrade to K 1.5.12. K 1.5.6 has its own problems and many of those were fixed with the latest version. Further, our recollection of the "peculiarities" associated with older versions (such as things that were used 12 months ago) is hazy these days and we don't always have the answers that might help you.
The second piece of advice is to look at the sticky topic in this
K 1.5 Templates and Design category:
Before you ask for help with template issues ...
because this probably answers the majority of these kinds of questions about the general layout.
As you will probably discover, most questions about the general layout - the "sizing" question that was asked - have their root cause in the choice of Joomla site template. Choosing the right template, one that suits
Kunena best for your site, is really the issue.
Again, as I have not seen the website we're discussing, we can really only give very general, broad answers.
Please review your question, in light of what I have just written, and consider how we might be able to better help you.