We address the problem of reliability of a finite-chain technique for
CsNiF3. We investigate the effect of the boundary conditions, complete
ly neglected so far, and apply a new extrapolation procedure appropria
te for quantities showing non-monotonic behaviour. From a detailed ana
lysis of the specific heat existing theoretical estimates for the mode
l parameters are discriminated and a strong evidence for the reliabili
ty of the direct finite-chain technique predictions is presented.