The problem you're having is not the size of the carb, but the style of carb.
A SHA carb is meant to work on a stock moped in a narrow RPM range.
Your stock Peugeot rarely goes over 8K RPM's, so a single jet carb with a pre drilled idle circuit works fine.
A carb with a needle and tunable idle circuit is a must if you're trying to tune the broad range that your engine is capable of.
In the Two-Stroke Performance Tuning book by Graham Bell, he recommends a 24-29mm carb for anything from 50-62cc's. This seems crazy high to me, but his charts are showing hp peaks way up around 13K rpm's.