I hit mid 40s with 16/45 which is almost the same gear ratio.
If it's sluggish on low end, definitely change clutch springs to at least blue. You also may be a jet or two rich. Check your plug.
Also, your needle position as you've described is 2nd from most rich, not lean. If the needle is oriented as it sits in the carb, bottom is rich and top is lean. Think of it this way - you pull the throttle and less needle stays down if your clip is at the bottom, which richens your mix.