Motivated by the closest major merger, the Antennae Galaxies (NGC4038/4039), we want toimprove our genetic algorithm based modeling code Minga (Theis 1999). The aim is to reveal the major interaction andgalaxy parameters, e.g. orbital information and halo properties of suchan equal mass merger system. Together with the sophisticated search strategy ofMinga, one needs fast and reliable models in order to investigate the highdimensional parameter space of this problem. Therefore we use a restrictedN-body code which is based on the approach by Toomre & Toomre(1972), however with some refinements likeconsistent orbits of extended dark matter halos. Recently also dynamical friction wasincluded to this code (Petsch 2007). While a gooddescription for dynamical friction was found for mass ratios up toq = 1/3 (Petsch & Theis 2008), major merger systems were only imperfectly remodeled. Here we show recentimprovements for a major merger system by including mass-loss and using NFW halos.