Boot with the following in the loader environment:
```
set debug.witness.witness_count=0
```
```
set debug.witness.witness_count=49152
```
```
set debug.witness.witness_count=131072
```
Resulting calculated witness allocations are minimal, > 2.25 GiB, and > 16 GiB (the latter of which is larger than my largest phys segment on my dev vm).
Note that setting it to -1 or some very large value will still cause an overflow related panic. I am avoiding addressing that now to avoid adding even more complexity to validate a debug setting.