Start-Process, mklink and encrypted/stored credentials, oh my - powershell

Question

I am working on a way to create a Symlink as a standard user, to address the situation outlined here.
I have created a password file and an AES key as shown here.
And I have this code, which without the credential stuff, but run from an elevated ISE, works as intended, creating a symlink in the root of C that points to the created folder in root of C.
But, when run unelevated it doesn't create the symlink, nor does it throw an error of any kind. It acts the same as if there was no credentials in use.
$passwordFile = "\\Mac\Support\Px Tools\x_PS Dev\SymLink_password.txt"
$keyFile = "\\Mac\Support\Px Tools\x_PS Dev\SymLink_AES.key"
$user = 'Px_Install'
$key = Get-Content $keyFile
$credential = New-Object -typeName:System.Management.Automation.PSCredential -argumentList:#($user, (Get-Content $passwordFile | ConvertTo-SecureString -key:$key))
if (-not (Test-Path 'C:\_Real')) {
New-Item 'C:\_Real' -itemType:directory > $null
}
if (-not (Test-Path 'C:\_Real\real.txt')) {
New-Item 'C:\_Real\real.txt' -itemType:file > $null
}
try {
Start-Process -filePath:cmd.exe -windowStyle:hidden -argumentList:('/c', 'mklink', '/d', 'C:\C4RLink', "`"C:\_Real`"") -credential:$credential -errorAction:stop
} catch {
Write-Host "Error"
}
So, three questions I guess.
1: Is there any way to test the validity of the created credential? I used $credential.GetType and it returns
OverloadDefinitions
-------------------
type GetType()
Which may or may not be correct, not sure.
2: Is there something wrong with my use of Start-Process?
3: Is there a way to actually trap meaningful errors or is cmd.exe so primitive I am stuck checking to see if the link exists post Start-Process and throwing my own error?
I tried
$results = Start-Process -filePath:cmd.exe -windowStyle:hidden -argumentList:('/c', 'mklink', '/d', 'C:\C4RLink', "`"C:\_Real`"") -credential:$credential -errorAction:stop -passThru
Write-Host "$results"
and it produces System.Diagnostics.Process (cmd) which isn't so helpful.
Speaking of Windows 7, I just tested it in Windows 7/PS2.0, and it DOES throw an error, but in Windows 10 it doesn't. Gawd Micros0ft, can't you get your shit together, EVER? but, maybe a thread to follow. Also going to try getting credentials another way, to eliminate that variable.
FWIW, I tried NOT wrapping the argument list in an array, in fact I started with that. But it didn't work so I tried the array on a lark.
EDIT: So, trying it in Windows 7 does produce an error, which is Parameter set cannot be resolved using the specified named parameters. I also realized I needed -verb:Runas in there. Added that, and switched my credentials to use Get-Credential for now. But still getting parameter set issues. Sigh.
Edit2: Seems to not like -verb or -windowsStyle in Windows 7/PS2.0. The latter is no big deal I guess, but -verb is pretty much required to get this to work methinks.
Edit3: nope, seems not to like -verb in Windows 10 either. But I have it reporting exceptions now, so thats a form of progress.
EDIT4: getting closer. I now have this
Start-Process powershell -credential (Get-Credential 'Px_Install') -argumentList "-noprofile -command &{Start-Process -filePath cmd.exe -argumentList '/c', 'mklink', '/d', 'C:\C4RLink', 'C:\_Real' -verb runas}"
And it works, but it raises a UAC dialog, which pretty much makes it useless.