Hi Abbie,
Does your lo really stay up 5 hours between nap and bedtime?? WOW!
Switching schedules can be done, although depending on your lo you might want to approach it differently. Some los can handle just a cold-turkey switcheroo. Some, not so much. You can extend the time slowly, like 10 minutes each day until bedtime is where you want it to be. Most los seem to do ok with that sort of thing. You might have to insert a catnap in the late pm for a bit to round things out.
Also, I think that you should be prepared that it might not work. If the current routine is really working well than he might revolt against your attempts.