It is true Mr Guthrie about Special Construction. I Emailed Mr. O'Daly a number of rule questions over the last few months pertaining to a new bike I'm constructing. To paraphrase in a nut shell ... If it is not now legal in Modified it is moved to Special Construction.
Last years seat, peg, tank and wheel base restrictions have been removed from '06 forward. This puts the emphasis on safety and less on artificial performance restrictions.
A direct quote from Mr. O'Daly per Email, "If your running in the Special Construction Class, then you've got a race bike and were going to let race bikes run without a bunch of class restrictions."
Modified is still pretty much restricted by basic changes to a Production bike, but there is a class, Special Construction where most anyone can now race once through safety tech.
By the way Mr. Guthrie, I still have vivid memories of Jack Wilson cussing you under his breath about you "going after all his triumph records" back in the day.