You've got one up on me for a start - I can't do good carbon fibre, despite the tutorials I come across now and again.
As for tips - the way I tend to do it is move the decal around and just play with it until it looks good.
Numbers - you can get a nice outline by this method:
Start with the number at size 1.00 and position 0.00,0.00. Stamp, move right 4 points, stamp again and move down 4 points, stamp again and move left 4 points, then finally change colour and move up 2 and right 2 points. Then group and move and size as required.
For embossing - start with number at 0.00,0.00, colour white and stamp. Then move right (or left) 4 points and down 4 points, colour white and stamp. Finally move up 2 and left 2 points and change colour to the body colour (only works on solid colours).