We reconsider the two-dimensional model for CuGeO3 introduced previously [P
hys. Rev. Lett. 79, 163 (1997)]. Using a computer aided perturbation method
based on how equations we expand the 1-triplet dispersion up to 10th order
. The expansion is provided as a polynom in the model parameters. The latte
r are fixed by fitting the theoretical result to experimental data obtained
by inelastic neutron scattering. For a dimerization delta approximate to0.
08(1) we find an excellent agreement with experiment. This value is at leas
t 2 to 3 times higher than values deduced previously from one-dimensional c
hain approaches. For the intrachain frustration alpha (0) we find a smaller
value of 0.25(3). The existence of interchain frustration conjectured prev
iously is confirmed by the analysis of temperature-dependent susceptibility
.