i tried the smaller front sprocket also and found that you are gonna be shifting like a mother it actually gets to be annoying i now run a 15/42 and i love it on the trails
i think that if you are having trouble with bottom end power then you need to address the other issues rather than gearing start with compresion, possibly a shorter swingarm and single carb or low end pipes will help you more but it all depends on your riding type