Looks like you are well on your way to build a nice car. I love that you offset your rear weight. I do that myself to get the weight balanced on the rears the way I want. Some tidbits that I see (and it may not be perfect information; I'm not totally sure how the top racers build their cars):
1) My rails that go down each side are thinner. I believe they are approximately 1/8" wide. This is to save weight on the body. I think its a nice comprise between reducing the weight and keeping some rigidity in the body. Everyone will most like have a different answer, but I'm scrounging for every gram I can get.
2) I narrow both sides of my cars, so much so, the cars can be either left FDW or right FDW. The only thing that determines which side the FDW is on is the weighting. I do this to keep the car tight against the track. That is, when the FDW is riding the rail, I might have somewhere between a 1/16" to 1/8" between the other rail and the raised wheel. When narrowing, I'm considering two things: the bend in the FDW and the bend in the NDFW. We know the bend in the FDW is a positive cant and we know the cant alone keeps the rear wheels off the rail. But I want the car to be centered, so I narrow the FDW side of the car. I also know the NDFW will have a negative cant (e.g. canted so the bottom of the wheel is farther from the rail than the top) and turned slightly towards the rail to shield the wheel cavity. With this in mind, you can actually narrow the NDFW side as well. I'm sure this can be debated until the cows come home, but I have always found a tight car is a fast car.
3) Not sure if you can have washers or not in the Scout Class, but if you can not and there is no rule where it says the wheel must contact wood, get some PTFE film with an adhesive backing and stick it to both sides of the car. Its nothing more than a sticker (stickers are usually allowed), but it can be polished. I have found it to be VERY VERY VERY close to washers in terms or speed. Skip the nail polish, CA glue, and all of the other tricks you may see people using in lieu of washers. This is faster and easier.
This is what I readily see in the body alone, but don't try to incorporate every trick at one time. Build a car, test it, and write down what you can improve upon next time. In 5 years of league racing (I'm new more or less starting in 2014), I have yet to build a car I'm completely happy with. There was always something I could improve upon. There are times where I seemingly drop out for a while, but in reality, I'm downstairs making a pile a wood attempting to perfect my next build. I'm always downstairs racing myself, but now-a-days, I'm finding it increasingly difficult to find more speed. There is a plateau where it become a battle of wills. I can say that there have been a number of occasions where my cars actually tied each other in time, to the 1/10,000th of a second.
Lastly, just have fun. For me, it's a huge stress reliever (well, until I get that car that just will not run; then I want to back to my day job).
