The engine does not care. When the top cam is in the correct position with the timing mark the valves are correct and when the engine cam is at TDC combined with the valve cam all is correct. I've broke a few belts in my day and never had a problem. As a small tip, you can loosely install the lower cover and crank pulley, set engine at TDC, remove cover and pulley and make some additional reference marks on the block. That makes it easier to determine if anything has moved without putting it back together. Additional reference marks on the valve cam also make life a little easier but always do your final check with a mirror using the engine marks. There are also some threads addressing belt installation you might find interesting. It involves instaling the belt one tooth off and setting the tensioner so everything lines up when the tensioner is released.