You can trim your locks to any length you want, but if they're still soft and not very tight, you might want to wait till they're more together before you snip so they don't unravel. But if they're pretty good and locked, then try snipping one or two from underneath so you can see what it might look like before you go for the top dreads. And maybe try snipping them at a slight angle, or on either side to form a 'v' so they don't look hacked straight across, if you want.