I picked up an emitter and spent an hour or so with the Mako, a multi meter, a RX-18 and finally the El Mod.

I tried just running the IR leads from the RX-18 through the Mako, aimed it at the Tammy M4, nothing. Then I hooked it up with all five leads, 2 IR, 3 BUs and as expected, it fired fine, so I worked my way back. Turns out, if the Mako input is grounded to the battery and the BU positive is wired to a 4.5 volt constant, when the signal given to the IR leads, it fires. I guess the chip needs power bsides the signal.

So, I rewired it all to the El Mod, using the Notek channel as the signal and it works like a charm. Under normal operation, the headlight is on with power, when you move the left stick down it switches to the Notek, turning off the main light. So, now when the stick hits the bottom (I'll reverse it to top) the IR emitter fires the Tamiya code. Five shots, one dead M4.

Now I just have to solder it all, finish the Ketten and sculpt a rider with a Panzerschreck.