I Can't recommend these enough for that fiddly type of flush or near flush cut..
https://www.carbatec.com.au/handtool...sh-cutting-saw
Edit: How did you go with the soft spot?
FrankenLab:
Turning tone wood into expensive sawdust since 2016!
MMM nice and smooth. Great job!
FrankenLab:
Turning tone wood into expensive sawdust since 2016!