 Shares of Thor Industries Inc. THO, 4.17 shot up 4.6 in premarket trading Wednesday, after the recreational vehicle maker reported a big profit beat for the fiscal fourth-quarter, as sales rose above forecasts and margins improved. Net income for the quarter to July 31 climbed to 280.9 million, or 5.15 a share, from 230.3 million, or 4.12 a share, in the year-ago period. 