First off hello i have a few questions to ask. This is mine and my sons third year in cub scouts bsa derby. First year we did ok .Last year we took second at our pack race that was a 32' wood track. Com was around 1". we built a new car for districts which was a 42' aluminum track. We moved the com back to 3/4 and the car was 5th out of 11. We use good wheels and axles and use tunstung weight. These are all stock wood and axle cut outs. Is there a difference on the com for different length tracks?And any tips would be nice. Thanks