Configuring 4 displays in a 2×2 grid?

I am going for the most minimal config I can, so my current config is this:

ThinOS
∨
General Settings
7 items configured
Configuration Item
Value
Group
Sign-on Settings
Domain Name
ewwylie
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Remember last username at logoff
No
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Disable Domain Field (8.5+)
No
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Remember last username and/or domain at reboot/shutdown
No
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Timezone
Manually Set TimeZone
No
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Date Format (8.5+)
yyyy/mm/dd
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Time Format (8.5+)
24-hour format
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∨
Security
37 items configured
Configuration Item
Value
Group
Sign-on Settings
Require domain login
Yes
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Disable guest users
No
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Require reentering password
No
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Require smartcard
No
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Icon Group Style
Default
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Privilege Settings
Privilege level
None
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Allow lockdown
No
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Show Display Settings (8.5+)
Yes
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Enable Keyboard and Mouse Settings (8.5+)
No
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Disable Date and Time Settings (8.5+)
No
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Admin Mode
Enable Admin Mode
No
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General Settings
Enable Gkey reset
No
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Enable Trace
No
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Remove Certificate (8.5+)
No
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Auto-install Certificates
No
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Disable ThinPrint Service
Yes
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Encrypt local flash
Yes
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Disable VNC Shadowing
No
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Fast Disconnect Key
No
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Security Policy
Security Policy (8.5+)
Warning
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TLSCheckCN (8.6+)
Yes
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Secured Network Protocol (8.5+)
No
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TLS Minimum Version (8.5+)
TLS 1.0
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TLS Maximum Version (8.5+)
TLS 1.2
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DNS File Server Discover (8.5+)
Yes
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VNC Settings
Enable VNC
Yes
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VNC Password
•••••••••
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Encrypt Password (8.5+)
No
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Max Concurrent VNC (8.5+)
0
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Zlib Compresssion (8.5+)
No
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Prompt user on start
Yes
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Query user timeout
10
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Prompt user on end
No
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View only
No
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Force 8bit
No
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WDM Service
Disable WDM Service
Yes
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Quick Mode (8.5+)
No
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∨
Display
12 items configured
Configuration Item
Value
Group
Monitor Display Settings
Monitors
Enable multiple monitors
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Multi Monitor Support
Screen ID
Monitor Resolution
Monitor Rotation
Align to Screen
Alignment
1
DDC
None

Top, Left
2
DDC
None

Left, Bottom
3
DDC
None

Right, Bottom
4
DDC
None

Right, Top
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Monitor Mode
Span Mode
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Main Screen
Screen 1
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Auto detect monitors (8.5+)
Yes
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Desktop Color Depth
32-bit
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Multi-Touch (8.6+)
Multi-touch
No
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Screen Saver Settings
Screensaver (8.5+)
15
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Lock the terminal (8.5+)
1
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Screen Saver Type (8.5+)

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Sleep (8.5+)
20
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Use Hours instead of Minutes (8.6+)
No

I will eventually configure more settings (like the default RDP settings, locking down the client, requiring NTLM login, etc), but those are non-issues if I can’t get the displays to work.

I don’t know how to find the firmware version, but the system version (maybe the same thing?) is 8.6_013. It looks like OS version 8.6_111 is available, and I’m looking at how to upgrade to see if that solves my issue.