Can't speak to Master Tow Dollies...but while our EZE Tow is lower to the ground than the typical Master Tow (shorter tires and no pivot pan), we have had no issues with rock damage to the toad in over 15,000miles of towing the car on the dolly.
But...the front of the dolly frame shows the signs of these miles in the powdercoat. No problem that a rattle can of matching paint doesn't fix.
Dolly towing puts the car up about 2 foot higher than flat-towing and away from these hazards, so it's not a big problem.
If you do add something to the dolly to prevent rock strikes, be sure the shield doesn't contact the car when at full steering lock.
Kim and Steve, Mustang LCDR (Ret), '07 Damon Outlaw #1193
I have seen gross intolerance shown in support of tolerance, Samuel Coleridge
WE LOVE OUR OUTLAW RV