There are many dose splits you can try. You did a 50/50 split. Maybe a 75/25 split or a 90/10 split would help you sleep better and give you all day pain relief.

Since you are on a 20 mg total dose ... Maybe 15 mg in the morning and 5 mg in the evening would be better. That would equate to a 75/25 split dose with the smallest portion always in the evening.