You know, the midpoint chart is a very useful tool. It represents the "relationship" as an entity in itself. So it follows a lot of the rules that natal astrology follows.
and you can put the transits on it to see which areas of the relationship are stressed or lucky at any time.
Plus...you can ALSO....print out the composite and put in the natal planets of each (separately) on the composite to see which person adds to or relieves the pressures of any part of the experience of the relationship.
For instance, if the Jupiter of one falls in an otherwise empty house in the composite that is meaningful. If a heavy planet falls on a major aspect pattern then that validates or intensifies that pattern....whether for good or not.
If the Jupiter or sun or Venus of one falls on the ASC of the composite that will lighten the tone of the relationship.
YOu can do with with the natal positions of both parties.
this is a really helpful way to figure out why something doesn't go smoothly even tho the composite might seem pretty good or neutral. And if you add the transits, and see what stressors may be afflicting each of the individuals, you can ascertain if the problems are likely to be temporary or not.
I have to add this tho: usually when there is a problem in a relationship there will be 3 or more "clues" as to why this is so. There will be issues in the synastry which are clues; there will be clues in the composite and there will be additional clues by adding transits to the composite or aspecting the natal planets of each party to placements in the composite.
It is never just ONE issue. Although if something keeps showing up....negative placements of Pluto, Neptune, Uranus or even MOON in all the charts, then this is an issue bigger than the couple involved.
LIN
PS: I have to warn you tho: compatibility is a very serious and complicated matter. And once you see major issues (Pluto, Neptune, etc) you cannot UNsee them. ) so compatibility study is only for those who demand to know the truth.