[FieldTrip] Common beamforming filters for different groups?

[Pomper, Ulrich]

Dear list members,
I want to compare source data between two different groups (patients and controls). Each patient has an age and gender-matched control. 
Is it correct to compute a common filter for each pair of subjects? The TF-topographies do look different within each pair, so I would assume that the sources are somewhat different. However, as I'm going to statistically compare the two groups it would be nice to have common filters, as otherwise any finding could be due to different filters as opposed to different sources.

Any help with this issue is greatly aprreciated!
Cheers, Ulrich