In retrospec the IR range limiting ideas are an inexpensive ways for Heng long battlers to add different classes to their battles. As all Heng Longs are five hits and you are out, you could use this simple idea to differentiate weight classes.

This caters to the market that doesn't want to spend $500 on a tank. Now you can buy a stock IR Heng long, spend $3.00 more for a harness and resistor, and have the ability to change weight classes via emitter range.

I think I'll promote this idea for Heng long users. I could easily make up cables that are plug and play, and supply 3 resistors for different ranges. It would be a patch cord that all users could simply use.