Free Return Trajectory

[Scimajor]

I'm trying to setup a simulation demonstrating a "free return trajectory". I've got the Earth and Moon system loaded and I put a small asteroid in orbit the same inclination and orbital plane as the Moon but I'm finding it pretty darn tricky to get the parameters spot on. I'm pretty certain at this point that I'd have to enter some actual data from an Apollo mission to get the parameters just right. Trial and error is not working particularly well.

Any suggestions?

[vh]

the best i've managed to find after a couple minutes on google is this: http://history.nasa.gov/SP-4029/Apollo_18-24_Translunar_Injection.htm
Is free return trajectory a very precise trajectory? if so, there will be a need to turn the time step lower.
also this page seems helpful
http://www.braeunig.us/apollo/apollo11-TLI.htm