The worst part of the dilemma was HPI mis-labeling a product as 5 x 50mm on the header card (3 different ones I bought were all marked as 5x50) that were actually 6 x 45mm, which isn't even close...that wasted months of time before it was discovered it wasn't just mis-packaged, the package itself was incorrectly labeled.
Anyway, I'll update soon with pictures and full description of the recipe, but Thunder Tiger P/N PD8967 is a pair of axles that are almost the exact same length as stock Buffalo axles, but have a standard 5mm shaft with cross-pins, not the taper-fit that's so difficult to attach aftermarket wheels to.
http://shop.towerhobbies.com/cgi-bin/wti0001p?&P=WR&I=LXALRR
There are some obstacles to overcome but nothing that requires major modding. You'll need to change to bearings with a 5mm I.D. but I already had plenty of those lying around. You'll need thick 12mm hexes with a 5mm hole, something between 6 and 10mm thick perhaps. You'll need to make your own cross-pins from wing wire (1.5 - 1.7mm thick) as these axles' cross-pin holes are not quite 2mm in diameter...or alternatively, you could drill out the holes to 2mm. Ideally you'll need about 1.5 to 2mm spacers with 5mm holes to keep the outer bearings in place in the hubs. All of that is easy stuff.
The bigger challenge is that the Buffalo requires wheels that have a major negative offset in order to clear the chassis. This is the opposite of most aftermarket wheels these days. This could be resolved by finding even longer axles & thicker spacers accordingly, or simply finding wheels that don't have much or any positive offset. (That means you need deep-dish style wheels, where the wheel width goes outward from the center of the wheel, not inward on the inside of the wheel.) For more explanation of offset, if you're interested, read here:
http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101
Anyway, I've found that 2.2" narrow crawler wheels typically have this kind of negative offset, and I can mount these wheels directly to the Thunder Tiger axles with only the mods aforementioned. I want to see what I can do to mount more common aftermarket wheels, so I'll update later.
