[Savage GT]

I have 4 RS cars, and I have found a way of tuning them that I like, that's not to say its the best way, but its what works for me.

The noise of the floating metal chassis, I don't find a problem, there are a few tutorials on the internet dealing with that if it bothers you.
To me that is the way its designed to work, and it works well.

First step is disassemble everything and check all mating surfaces are free from burrs or imperfections in the coating. 
On my 4 cars, all have been fine which speaks well for the QC in my experience, but if you find any imperfections carefully file them flat (or in the case of burrs at the edge of holes use a suitable cone dremel piece or larger shallow angle drill bit by hand to clean up.

Reassemble the axle stands first, leaving the screws finger tight  then test the axle stands opposite each other are in alignment, this tip I picked up from, I believe, one of Tamar's posts. You will need a dead straight piece of 6mm rod around 50mm long for this.
With the bearings from the axle stands removed (in most cases these come out easily) check the rod can freely slide between the posts then tighten fully and recheck.

Once that is set, reinstall the bearings, if they are not a tight fit, you can use a thin smear of non permanent glue or thread-lock on the inner wall of the axle post to fix in, being careful not to get any on the shoulder or moving parts of the bearing !

I then put a drop of thin oil with a needle dropper on the bearing face, and inside where the axle will go. then install the rear axle, gear and opposite side wheel as you would normally, leaving just a whisker of lateral play.
I like my gear to be as inboard as possible, so I use the smallest spacer I can between the gear and bearing. 
I used NSR guide spacers as these are readily available and come in 0.12mm upwards thickness. There may be specific 3mm axle spacers available for this but working from my 1/32 specific spares supply these fitted and were at hand ;)

If you want to change the pinion to alter gearing, I use the Slot.it 6.5mm anglewinder gears, note that the stock gear fits onto the motor shaft a little under flush so replicate this. 
Next, I fit the motor mounting loosely on the chassis too allow it to slide, and the motor to this tightly, remembering to include the metal plate supplied in between the motor and pod.
Then I use a rizla paper between the gear and pinion, slide the motor up and tighten the screws. Remove the rizla paper and check for a good mesh, tweak if needed.
Once I am happy with the mesh, I usually run for 30 secs in each direction dry, then lube the gears with your preferred gear lube.

Refit the front axle and wheels/spacers oiling as above.
Either refit the guide, or the supplied deeper guide, with spring depending on your track. 
I replace the braid with NSR 0.2mm but this is personal preference.
For copper tape (or plastic track where the rails are fractionally above the track surface) I leave about 1mm of upward travel in the guide, for braided track or others where the rails are below the surface, adjust to suit.

Check all tyres are fully seated on the rims, you can glue and true if desired but for home use on my copper tape routed wood track I have not found this necessary with stock tyres.

Because I like a bit more float than standard, I use the alternative RS chassis T-nuts and screws.
I light smearing of light grease or oil on the T part of the nut, or hole it goes through may help, but isn't strictly required.
Usually RS use spacers to sit the wheels flush with the arches, but if you want more float like me, you may need to get smaller spacers, or trim the supplied ones down for the rear to allow clearance.
Because the way the chassis is designed the fronts move with the body so can stay flush to the arches.

Finally, if you want to adjust the height of the body as it sits in relation to the wheels, either for more float clearance, or aesthetic purposes, I use neoprene washers under the rubber boots on the body posts where required. 

I find the best way is by removing the rubber "boot" and sliding it over my NSR 0.9mm grub screw tool with the cup side to the tip, then slide the neoprene washer past the hex tip onto the shaft and use the tip to guide into the body post hole. Then slide the "boot" all the way over the post dragging the neoprene washer with it.
This ensures the washer sits in the right place and the nature of the rubber and neoprene ensures they will stay put while you put the screw in and tighten to just past finger tight.
Some may want the body screws a little loose to enable slipping the body off without unscrewing, others a neoprene washer between the screw head and chassis for further damping, but I find it fine for me as I described.

Hope this helps those new to the RevoSlot cars, and anyone with further suggestions or tips, feel free to add your thoughts.