The formation of Kuiper-belt binaries through exchange reactions

In the article in Nature Vol 427 of 5 February 2004
"The formation of Kuiper-belt binaries through exchange reactions"
Kuiper-belt binaries with masses m1,m2=1 are explained by the
introduction of a third much smaller object of mass m3=0.1
I agree with this approach, however I have certain doubts
about the details.
Specific the causes like:
"through tidal disruption of one object followed by coagulation
of fragments during a close encounter with the other" and
"a giant impact, where collision debris coagulates into a moon".
There are two questions to answer:
1. What is the chance that two masses like m1,m2 meet each other
2. How many more masses like m3 are there compared to masses
like m1 or m2.
In question 1 I do not mean binary masses but two masses which
move in almost circle trajectories around the sun.
In general when those two masses meet they will not form a binary system
(Each path however will be modified, allowing for future interactions)
however when a third object is there simultaneous, all different
scenarios are possible.
For more detail see my url:
http://users.pandora.be/nicvroom/slingsh1.htm
From that link there is also a program available
which allows you to simulate the different scenarios

Nicolaas Vroom
http://users.pandora.be/nicvroom/