Found another discussion in these forums that is related, and it looks like LucD pretty well answered my question already. A bit more experimentation yielded the following, which was successful, although a bit ugly:
PowerCLI C:\Scripts> Get-OSCustomizationSpec -Name $customization | New-OSCustomizationSpec -Name tempcust -Type NonPersistent
PowerCLI C:\Scripts> $osCust = Get-OSCustomizationSpec -Name tempcust | Get-OSCustomizationNicMapping | Set-OSCustomizationNicMapping -IpMode UseStaticIP -IpAddress $ipaddress -SubnetMask $netmask -DefaultGateway $gateway -Dns $DNS
PowerCLI C:\Scripts> New-VM -Name $servername -ResourcePool $clustername -Template $templatename -OSCustomizationSpec $osCust