Mapping between US and French tennis ranking system

I live in France and read a lot Tennis Warehouse Talk Tennis message board. I see sometimes players give their ranking in message boards and would like to get an idea about what the level of tennis they play. My actual French ranking is 30/3. I hope that someone, who lived and played in both countries, can help me map those two systems.

All I know is the following:

Ranking pyramid in US starts from 1.5 and goes up to 7. Level 6 player often has national ranking.

In France it starts from 30/5 and reaches 0, then goes to negative values where you will find national level players. The pyramid looks like this: 30/5, 30/4, ..., 30/1, 30, 15/5, 15/4, ..., 15/0, 5/6, 4/6, ... 1/6, 0, -1/6, ..., -15. French system uses handicaps.