I noticed an interesting and simple modification while watching this year’s 24 Hours of Daytona – a couple of the DP teams had strung a length of surgical tubing from the cabin roof to a loop of tubing wrapped around the shoulder belts of their harness, above the adjustment buckle. This keeps the harness belts within reach when getting into the car and pulls them out of the way when the lock is released (especially handy when trying to get out the car quickly with a HANS on.
For all I know, this may be a well-known trick, but it’s the first I’d seen of it.