I first got the idea for this over on the thread for the DX6/7 on RCGRoups.com forums. I run nitro cars, so I bought a DX3. I used the radio for a while, and my battery life was on the better side of most radios--but the DX7 owners were getting like 5-6 hours of runtime after the mod. Now that's what I'm talking about! I figured that the DX3 and the DX6/7 might be using the same regulator chip, due to the fact that the chip design and internal circuitry shoulden't have changed that much. Less PCB tooling and all that.
Turns out, I was right.
I would harbor a guess that the DX2 (new and old) use the same regulator inside. However, I have not tested those and the innards may be a little different. Check your parts, and make sure your soldering it in the right way. Best case, it doesn't work. Worse case, you release the factory-packaged smoke and you get to buy a new radio. Not fun.
The mod is about as easy as it can get: De-solder a component, tin the pads, put the other component on. Done.
Here's a picture-by-picture diagram on what to do. As with everything on the Internet: I take no responsibility on your actions. This worked for me. It may not for you. Don't do it if you can't solder.
Step 1: Assemble your tools
Step one: Assemble your tools. As with any good mod/hack, get your tools together before you start modding. Also a good rule for life, I suppose... At any rate, I ended up using:
Needle Nose Pliers
Solder, sponge, etc.