I don't know whether I'm getting this right.
In my understanding, the benefit of a large stripe size lies in parallelisation: Suppose the stripe size is such that a file system block fits on a single disc, i.e. stripe size = (file system block size)*(number of "effective" discs). Then, if one (read) transfer makes disc A seek to block X, there is a good chance that the next transfer can be satisfied from disc B != A, making disc B seek to block Y in parallel. Or will this (issuing requests to different discs in parallel) not happen on NetBSD?