We investigate two simple prescriptions to account for the Pauli principle in
a three-body cluster model employing a new method based on an adiabatic
hyperspherical expansion to solve the Faddeev equations in coordinate space.
The resulting wave functions are computed and compared. They are furthermore
tested on halo nuclei by calculations of momentum distributions and invariant
mass spectra arising after fragmentation of fast 6He and 11Li in
collisions with light targets. The prescriptions are very accurate and the
available measured quantities are remarkably well reproduced when final state
interactions are included.Comment: 18 pages, LaTex file, 15 postscript figures included using epsf.st