Ok Taj.... here goes for a little guide

There is no kit AFAIK for the Matrix.

I never said it might work, it will work. I have already been using version 1 of the conversion and in this week, will be finalising version 2 if all goes according to plan. I've converted a few RCs and my last completed one is my HPI Firestom which made it all the way to version 3, check it out here (you may need a translater in your browser): http://www.rcgalleri.dk/galleri/4782..._10t_brushless

Sorry for the picture quality, took them this morning just before shooting off to work.

In pic 1, you can see how I expect to mount everything. I've chosen this way to try and balance the weight as best as possible. Motor ca. 500g, batteries ca. 800g, ESC ca. 100-200g(?) etc etc. The ESC is the same as in my Firestorm. An el cheapo 100A 4S ESC from hobbyking.com - of course you buy the ESC that suits your style.
For this setup, I will be reverting to the CEN 66T spur as space is tight with where I want the motor installed. I will be using a 66/16 gearing, it's close enough to the 46/12 gearing for me. The Vorza motor mount accepts up to 4274 motors. I am using a Leopard 4092 1480kv motor so I grinded the rear mount tab to make space for the longer motor. Since the pinion will be mounted rather far down the shaft, I've opted for the Tekno long shank pinion for added strength.

As you can see in pic 2 below, this is the current setup where the motor is on the opposite side to the battery case. The ESC and receiver were mounted in front of the battery case. Now, the guy who did this not-so-nifty work didn't think things through. With this setup, the gearing was 46/12 as he used a Vorza spur gear. Note that the batterybox in the picture is just as an example, I will definitely be using the Vorza battery box.

For tools and odds and sods you need:
3, 4 & 5mm drill bits
Tapping drill bits for 3, 4 & 5mm screws
Oodles of loctite
4mm countersunk M screws - probably 6-8mm in length

Here's how I plan on doing it:

1. put the motor in the mount and clamp it down. Install the pinion.
2. line the motor up with the spur and (yep, you need to be careful here) get a good mesh. Make a mark for the front mount hole under the pinion and draw a line along the outer edge of the motor mount.
3. Drill and tap the hole. Remount the motor mount, line up with the line you drew and mark the 2nd hole at the rear. (here you need to check the mesh is still ok) Drill and tap. Then you can drill and tap the last 2 holes easily. If you f**k up when drilling the first 2 holes, then you can make the holes longer so you can slide the motor mount - just requires a bit more work and a dremel to make it look real good. As I don't expect to screw it up I'll be using a countersink drill to ensure the screws are flush with the underside of the chassis.
4. Mount the battery box on the diagonally opposite side to the motor.
5. I've found that the Traxxas mamba ESC brace can fit over the HK 100A ESC if I just re-solder or jimmy the fan wiring. So I'll be doing this so I can drop strips/zip-ties(?) round the ESC, which NEVER last me long anyway. If you go for the Mamba motor set, well, then sir, you have a wicked set and the brace fits perfectly. Drill and tap and install on the same side as the motor. I expect to mount my receiver in the same area.
6. As per pic 2, you can cut and shorten the servo mount.
7. Zip-tie/strip/tape-down the wiring and make everything look good.
8. Whoa...what happened there...? YOU'RE DONE!!

I've added links to Tower Hobbies for you so you should be able to get everything from one place. I guess their postage is cheap/free within the US? Even over here to Denmark their rates are ok.

If you or anyone else has any questions, feel free to ask. Also, if anyone has any comments or better ideas for the conversion, let me know. I'm not religious about the end result, except it must look good and function well and be as balanced as possible.





Vorza motor mount:
http://www3.towerhobbies.com/cgi-bin...&I=LXZXL8&P=ML

Vorza Battery box:
http://www3.towerhobbies.com/cgi-bin...?&I=LXZXN2&P=7

Long shank pinion:
http://www3.towerhobbies.com/cgi-bin...?&I=LXZBK4&P=7

Traxxas brace for Mamba ESC:
http://www3.towerhobbies.com/cgi-bin...&I=LXXFD3&P=ML