Besides upgraded motor assemblies, waterproofing structures, steering structures, tail lights, camera mounts, the big improvement since 2024 was a new transmitter & radio set.  The radios changed from raw RS232 to PWM.  Time differences between level transitions determined a 1 or 0.  The bitrate was reduced from 100kbit to 25kbit.  A new transmitter & charger were made, with more antenna exposure, more room for a bigger battery, more audible speaker position.

Split the circuit into a charger board & radio board.

A mix of clear & grey filament made an appealing case, but any future clear PLA was abandoned.  It lead to overheating in sunlight & was too brittle.

It was found that the antenna could be optimized by measuring the transmitter current.  The receiver & antennas could be adjusted by plugging them into the transmitter.  The density of a coil changes the electrical length independent of the length of the wire.  This led to some antenna changes which made the biggest improvement in range but also increased battery usage.  

There was an effort to improve the reception by oversampling the PWM signal in a really fast microcontroller.  It didn't make any obvious improvement that would justify the cost, because the hardware already does schmidt triggering.