Hmmm. There are astrologers that work with harmonics (
see here) but I have done no work in this regard. It was pointed out to me by a BL astrologer that I have a rather interesting 9th harmonic chart; it's thought that the 9th harmonic has a relationship with Pluto and Plutonian themes. I kind of dread the use of the term "soul mates"... this is part of my "homework" this week, so I'll return once I've finished that lesson. My own 9th harmonic chart gives Sun and Mars in Scorpio, AC at 2 Virgo (I just can't shake that damn Virgo Asc!) and chart ruler Mercury once again in Aries. Mercury is in an out-of-sign trine to Mars and Venus is conjunct Jupiter in Capricorn. The differences to my natal chart are pretty astonishing; there might be something to this. Mars seems very happy in Scorpio. Pluto is at 2 Aries. I've always felt much more like a Scorpio than an Aries. I would post the chart but I need to rotate it so that the Aries Point isn't by default on the Asc (this makes it difficult for me to read) -- astrodienst is sucky like that.
Regarding sidereal v. tropical: I've done 99% of my work in tropical, so I'm probably among the least qualified to comment. My own sidereal chart is loaded with Libra and Sun is at 0 Aries; Moon in an out-of-sign conjunction at 27 Pisces. I have used the Fagan-Bradley, not the Lahiri, sidereal method. I have heard that sidereal is best for predictions and that transits to the sidereal chart should be looked at carefully. Again, much more research on my part required. But anyone who knows me well can probably vouch for the fact that I don't exactly exemplify Pisces Moon.

I'm skeptical on that alone