Sorry but in my opinion that is the wrong way to do it, you should use a supporting page for a detail page as illustrated in all included features in mojoPortal that have detail links or use their own friendly urls. This problem is a good example of why this is not the right way to do it. Modules should be designed to play nice with other modules on the CMS page which means they don't own the page and should not manipulate the url of the CMS page with new parameters.
See the Blog feature, it has a list of posts on the cms page but individual posts link to a detail view that is not the CMS page, ie the friendly urls point to ~/Blog/BlogView.aspx?pageid=x&mid=y&ItemID=z not to ~/Default.aspx with extra params.
You are trying to re-use Default.aspx for things it was not intended for, it is the CMS page and it will use the canonical url of the current CMS page.
I recommend re-factor your feature to use a supporting page where you have complete control over the page and update your friendly urls to point to your supporting page.
Hope that helps,
Joe