A heat transfer sheet assembly for a rotary regenerative heat exchanger, comprising: a first sheet element having a first profile comprising a plurality of parallel and elongate first and second sheet spacing features (21, 22) extending longitudinally in a gaseous flow direction, with a first repeat of said first profile being defined between and including immediately adjacent first and second sheet spacing features (21, 22); and a second sheet element of equivalent length having a second profile comprising a complementary plurality of wide gauged, parallel and elongate third and fourth sheet spacing features (23, 24) with a second repeat of said second profile being defined between and including immediately adjacent third and fourth sheet spacing features (23, 24), the first sheet element being packed against the second sheet element with said first and third sheet spacing features of respective matched pairs of said first and second sheet elements and said plurality of second and fourth sheet spacing of the respective matched pairs seating against one another to define for each said matched pair a generally close sided elongate channel for gaseous flow therethrough, the first sheet element having lobular heat transfer undulations extending laterally and uninterrupted in between each of the first and second spacing features, the second sheet element further comprising a respective elongate fifth sheet spacing feature extending longitudinally along at least half a length of the second sheet element, intermediate the third and fourth sheet spacing features of each said matched pair, each fifth sheet spacing feature comprising a lobe, the fifth sheet spacing feature lobe having an amplitude less than or equal to a spacing provided by the seated first and third sheet spacing features and the seated second and fourth sheet spacing features, characterized in that the fifth sheat spacing feature lobe contacts at least some of the lobular heat transfer undulations between the first and second sheet spacing features of a respective matched pair. a first sheet element having a first profile comprising a plurality of parallel and elongate first and second sheet spacing features (21, 22) extending longitudinally in a gaseous flow direction, with a first repeat of said first profile being defined between and including immediately adjacent first and second sheet spacing features (21, 22); and a second sheet element of equivalent length having a second profile comprising a complementary plurality of wide gauged, parallel and elongate third and fourth sheet spacing features (23, 24) with a second repeat of said second profile being defined between and including immediately adjacent third and fourth sheet spacing features (23, 24), the first sheet element being packed against the second sheet element with said first and third sheet spacing features of respective matched pairs of said first and second sheet elements and said plurality of second and fourth sheet spacing of the respective matched pairs seating against one another to define for each said matched pair a generally close sided elongate channel for gaseous flow therethrough, the first sheet element having lobular heat transfer undulations extending laterally and uninterrupted in between each of the first and second spacing features, the second sheet element further comprising a respective elongate fifth sheet spacing feature extending longitudinally along at least half a length of the second sheet element, intermediate the third and fourth sheet spacing features of each said matched pair, each fifth sheet spacing feature comprising a lobe, the fifth sheet spacing feature lobe having an amplitude less than or equal to a spacing provided by the seated first and third sheet spacing features and the seated second and fourth sheet spacing features, characterized in that the fifth sheat spacing feature lobe contacts at least some of the lobular heat transfer undulations between the first and second sheet spacing features of a respective matched pair.