The POINT-AGAPE collaboration is currently searching for massive compact halo objects ( MACHOs ) towards the Andromeda galaxy ( M31 ) . The survey aims to exploit the high inclination of the M31 disk , which causes an asymmetry in the spatial distribution of M31 MACHOs . Here , we investigate the effects of halo velocity anisotropy and flattening on the asymmetry signal using simple halo models . For a spherically symmetric and isotropic halo , we find that the underlying pixel-lensing rate in far-disk M31 MACHOs is more than 5 times the rate of near-disk events . We find that the asymmetry is increased further by about 30 % if the MACHOs occupy radial orbits rather than tangential orbits , but is substantially reduced if the MACHOs lie in a flattened halo . However , even for haloes with a minor-to-major axis ratio q = 0.3 , the numbers of M31 MACHOs in the far-side outnumber those in the near-side by a factor of \sim 2 . There is also a distance asymmetry , in that the events on the far-side are typically further from the major axis . We show that , if this positional information is exploited in addition to number counts , then the number of candidate events required to confirm asymmetry for a range of flattened and anisotropic halo models is achievable , even with significant contamination by variable stars and foreground microlensing events . For pixel-lensing surveys which probe a representative portion of the M31 disk , a sample of around 50 candidates is likely to be sufficient to detect asymmetry within spherical haloes , even if half the sample is contaminated , or to detect asymmetry in haloes as flat as q = 0.3 provided less than a third of the sample comprises contaminants . We also argue that , provided its mass-to-light ratio is less than 100 , the recently observed stellar stream around M31 is not problematic for the detection of asymmetry .