The estimators under consideration are: F3SLS, M3SLS ai., i W351.S proposed by G. R. Fisher, A Madansky and M. R. Wickens respectively, It is shown that better estimates of correlation between residuals of differeent structural equations (fu) will lead to better estimates of structural parameters (a, $) in small samples. Solutions to the problems of computational difficulties, due to the estimation of fu are also given.