1. base  Squeak3.8-6665 image.
2. open squeakmap
3. load Balloon3D
4. load PackageInfo (apparently update from 16->18). It recommends loading Monticello, which I do (v 231).
4. save image.
5. Open Monticello browser and load VMMaker38b4.
6. save
7. file in GCInstrumentJMMImprovementsAR.1.cs.
I get a warning that FloatProto is still used in ObjectMemory.
8. save.
9. file in JMMGCMonitor.4.cs
10. save.
Crash.  Looks same as before.

Theory: JMMGCMonitor should only be used with VM's built with
GCInstrumentJMMImprovementsAR.

So perhaps I should try again, skipping step 9?

And then build the VM?  I was not going to do any editing of the
VMMaker code in this new version.

What about the FloatProto warning?