I had to do a similar operation with both my EXA-1 and ESR-1.
I opted to put a saw cut down the end of the neck heel, then use files and sanding blocks to tidy up. Generally less stressful, as if you aren’t confident in the saw cut, you can mount it in a mitre bloc to insure you get it square and perpendicular to the tenon.
I hope yours didn’t cause too many conniptions!