Co-exist with Loggintoboggan?

I need LoginToboggan for a few reasons on my site, and one of it's nice features is for anon users, if the user gets a 403 page, it'll take them to a logintoboggan custom page (saved on the 403 line in error settings) with a login form on it.

However, users still get the standard 403 error page if they are logged in (authenticated users). From what I can tell, in order for users to see the CustomError page, customerror/403 needs to be added to the 403 line in error settings. What I'd LIKE to do is maintain the logintoboggan behavior while still being able to add my own custom error page for the authenticated users. Is this possible?