90 degrees is severe. We can usually keep to a straight line by trimming the mainsheet or the traveller (which depends on windstrength and how strong your mast is). Driving fast downwind with the spi is not just about going as high as you can. The idea is to build virtual wind and drive off down towards C mark with the virtual wind. Watching the Tornado pros do this is just awesome! 10 degrees lower and faster than the rest <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> When driving off you need a good feel for the wind and compensate main-trim or course early to keep the windward hull stable. Practice is the only way to go to develop the feel for your boat under different conditions.