There's not a whole lot of secrets to making these trucks work well, even on black carpet. Most of them have already been mentioned in this thread numerous times-
1. Glue the very edge of the sidewall. There's a texture on the tire in the area that I'm referring to. This helps on both grey and black carpet.
2. Water dip the motor to break it in.
3. If bearings are the only hopup, remove the grease from them and use really thin bearing oil.
4. Don't just slap the kit together. Just because it's a cheap kit doesn't mean that it deserves a cheap build. Make sure that everything rotates and moves freely like you would with any other racing kit.
5. Drill the body holes so that the body can float around on the post.
6. On the front body clips, don't use the hole closest to the body. Use one hole up so the body can bounce without taking the chassis with it.
Bonus tip- Don't overdrive the things. You can't pitch these things into a turn or flog them around the track and expect them to handle like a regular touring car. Use the brakes and baby them through the turns. Smooth is fast.
I've tried the upside down shock thing, and the fluid still leaks out because the top end is still 3 pieces. Even with 100k in them, it really didn't help the handling compared to the stuff above. Also, the more the trucks are raced, the better they handle. I think it's the slop that develops absorbing some of the bouncing and vibrations. My son's truck is about 6 months old, and it handles great. People at Minnreg kept asking me what I did to the truck to make it handle and stop bouncing this past weekend, but I haven't done anything other than the info above.
K.I.S.S. method prevails in this class.
(My truck is the red/yellow/blue RedBull scheme)