Tow rope thimbles

What is the consensus of opinion of using steel thimbles on aero tow ropes?

Currently we use some clear tubing in the loop to protect the rope from wear of the Tost tow ring. Not only does this allow the rope to bend sharply causing a weak point but it also seems to fill with dirt. This then manages to find its way to the sharp bend in the rope where it grinds away at the rope (poly) and precipitates a breaking point.
A steel (or other hard material) thimble in the loop would seem to eliminate this problem and look a lot more professional too.

Anyone out there do anything different or profess not use thimbles?

Bob 7U