Hi alan -
The wheels (which require welding them on, by the way...) only prevent the most gruesome of nose-scrapes - they will prevet the kind of damage that would be caused by , say, driving out of a steep downhill driveway to an abruptly-flat road surface - where the radiator supports would contact the ground before the nose would etc.
In other words, they only protect against a particular kind of abrasion.
Many swear by them - I get by on my instincts and refusing to navigate anything that looks like a "tank-trap".
As for the chin air-deflector (gm's terminology fo the piece).
It is designed to deflect and rotate under if it makes severe contact with anything, and it does pretty good at this.
The small metal brackets that hold it on the car (with two bolts) are prone to bending, but at the same time, they are easily bent back into shape.
And, as Tammy points out, it is a fairly inexpensive part to replace if it becomes so tattered as to be noticeable or a worry - I bought one to have as a spare for around fifty-bucks.
My opinion - just watch out for severe transitions in road surface, and I am not talking something that you would EVER see on an actual road, it would be on a driveway-to-road, or vice-versa, transition.
If you do feel the need for the "frame-savers", then here is a link -
http://www.corvettegarage.com/product/aa-frame-savers-for-c5-and-z06-corvette.html
You will notice in the installed picture on the above link that the wheels will still allow the air-deflector to make contact first , then the wheels....Oh, and it states that they can be bolted on , but that welding will make them more secure.
best regards -
mqqn