is this a sensible default? Looks like GDAL has it at 10 - I'm happy to increase the number, but how much did you need it to be for the tile in question to function appropriately? (link: http://geoinformatics.aalto.fi/doc/Geo-GDAL-1.9/html/class_geo_1_1_g_d_a_l_1_1_band.html#aa7431f1edacf0a7f4424d6f89fa851b5)