I have to say its a tough one, I modify my lr because I enjoy doing it and cos I can! So why should that affect me when it comes to entering comps. But it's not necessarily fair on people who dont.
Maybe they should have a class system... standard, modified but stll road legal and the full out unlimited class.
All the groups could either run at once and be grouped on a winner's list or run in seperat stages, that way theres still lots of people attending!