Tie rods - I was able to find ball and socket ends that screw onto nominally sized 2 mm "rods," all in on Amazon for like $20 to do this. It should work, I think, and take out any of the slop in that spot. Not sure if we can post links to e-commerce sites on this forum - but they have those rods in like 10 mm increments.

I don't think cutting a bearing down is feasible, especially in the lathe i've got. I tried drilling one for something a long time ago and it was not nice to bits. I didn't intend to imply that I'd modify the bearing. I think turning the axle down is the ticket, so long as I can chuck it on the hex and fit a tool in between there and the cup. If not, I'll have to find new cups and start from scratch. Replacing the nylons won't gain me a whole lot, as it sits. There is so much wear on the axles themselves that it would only be marginally better. the second inner nylon on my particular car rides on the very end of the drive cup. It just doesn't look like it was a great design to me from the start - lots of wear on cup and nylong both on this one from debris. I liked to put lube on everything when I was 12 because I was sure it would go faster. Well, other than protecting from rust, I can see the downsides to what was going on in my little brain.

Regarding the batteries, I was thinking that, at max, I might 3D print different pieces to put on and allow an 8.4 battery fit in, just or giggles. Yeah, I have learned about LiPo needing to be babied a lot. There are PCB's that are about a dollar a pop on ebay to protect against over-discharging. The other battery pack I mentinoed is one of those old Tyco "Flex Pack" deals, I can fit a 2S LiPo in a tray I drew/printed with the PCB along side it. I've got some ZEEE brand batteries and a balance charger coming from Amazon. I picked those due to budget, but you mentioning the LiPo dangers has me thinking to maybe look into a Traxxas battery/charger. It would cost about 2x as much to do, but would probably be 1/2 the risk in burning up. Have you ever used ZEEE brand batteries?

3D scanner...damn that sounds handy. I don't actually have a printer of my own, but a good friend of mine has a few of them and I've got pretty full access to use them. I just got the lathe last year. It's an old Atlas lathe. I've wanted one for years - there is some little bushing or shaft issue like this about once a month and it's nice to be able to just do it rather than looking for stuff that doesn't exist to hack something together. Old school, maybe...maybe partly insane? I'll be 40 this year but can't leave things alone. I'd be the guy that buys a 200 hp car and spends more money modding it to 250 hp than the 260 hp car would have cost to begin with.