Hi John,
you can use the next PowerCLI script for the reverse approach:
Get-Datacenter -name "Target Datacenter" |
Get-VM |
ForEach-Object {
$VM = $_
$VM | Get-VMResourceConfiguration |
Where-Object {$_.MemLimitMB -eq -1} |
Set-VMResourceConfiguration -MemLimitMB $VM.MemoryMB
}