Thanks guys. I had planned to make a cool movie of my Sherman shooting the truck and stopping it dead, but the IR LED on the Sherman is not working. I even had Oddball talked into doing a cameo appearance as the tank commander.
I can fix the Sherman, it's a Mato with a DBC slaved off a Heng Long RX-18 board that I built out myself, but it will take some time. I tested the truck target circuit using a stock Tamiya Leopard, a Heng Long Abrams with a IBU3, and a stock Heng Long T-90 with the 7.0 board. It worked great with all those tanks. Alas, the Sherman will take IR hits, but will not give them out.