NGROUPS/NGROUPS_MAX

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I need a certain user to be a member of (or, more precisely, have NFS access 
to the data of) more than 16 groups.
One way to go would be to use umapfs to map 16 groups to one.
Is it possible to compile a kernel with a raised NGROUPS or NGROUPS_MAX?
Is there any downside (apart from slightly higher memory usage)?