H506, take some wire and secure the rod off to the side. You want good, strong light to see in there.
Besides that, the back side of a #11 xacto blade shaves the leadloy metal nicely. I don't recall the turning speed...just feel it out for what works for you. Make the walls as thin as a playing card if you are having a good time at it.
The only caveat ..two possible negatives is if you make the piston too light then the engine will obviously let you know and you might have to grind a divot out of the crank's counterweight. I've never had to do this with a TD.
The other caution is the piston is easier to make out of round while doing a rod reset.
You'll want to make a nice little holding fixture out of hardwood or aluminum to hold the piston in the jaws of a lathe chuck.
If you ever get a chance to look at a "real" Killer Bee .049 they have a thin wall piston, but not quite as thin as you can go.