I think FvM is not wrong. In order to save simulation time and disk space you can do some approximation. That is:
rise time of 1st order (RC like)
taking the 90% of energy of the signal can be enough
under these conditions we know the rise time can be modeled as Vrise/Vmax = 1-exp(-t/RC)
defining now the rise time as 10% to 90% of Vmax (the final voltage) we will have
0.9=1-exp(-t1/RC)
0.1=1-exp(-t2/RC)
solving for time and combining the two equations rise-time≈t2-t1=2.2*RC
also we know BW=1/(2*pi*RC) then:
BW≈=2.2/(2*pi*rise-time) from which
BW≈0.35/rise-time or BW(MHz)≈350/rise-time(ns)
Using this method you don't reconstruct perfectly the shape of the rising edge (to do this you have to use the pancho_hideboo method), but I think you can get result accurate enough for the cross-talk modelling.