the partial coverage of EPI is intentional--we're scanning parietal cortex w/ hi-res epi sequence. this limits the extent of our coverage, but is plenty for what brain areas we're interested in examining.
the bulge is a ghosting effect, resulting from certain preprocessing steps taken prior to analysis. the functional data i eventually try to get onto the surface is masked by an ROI, so the bulge shouldn't become a factor (at least to the best of my knowledge).
after neuroscience i'll try to survey the problem more closely, and post anything i can find.