Finished basement question regarding trim on handrail
I'm nearing completion on my finished basement and I have a question with some trim on the stair handrail. I just put this handrail on and I'm trying to install trim to cover the gap between the sheet rock and the pine board. I bought some quarter round, but I'm having trouble figuring out the the miter angles to cut at the bottom.
The slope of the pine board is 42.5 degrees and the wall corners are standard 45s. I've tried different angles, switching the orientation of the quarter round but I still can't get it close. I included a pic so everyone can see what I'm trying to do. Any advice would be appreciated. Thanks