If, like me, you rarely cut steerers on threadless forks, either because you might one day want to fit the fork to another frame, or you suffer from back problems and might need to raise the bars at some point, don't pad the steerer out with spaces, no, instead put two stems on it. One points up, the other down. One takes your handlebars, the other takes a sawn off bar. Thus you can fit loads of bar furniture: computer, lights GPS, bar bag, etc with little trouble, and because they are at different heights the bar bag won't interfer with the lights.
As a used stem can be picked up for peanuts this works out both cheaper and stronger than a space grip.