I need help getting Impact and Optifine to run together. I'm really new to all this and might be taking an unnecessary step.

I'm using Forge to run Impact and Kami Blue together. I want to use shaders, so I've installed Optifine. 

 

I'm running:

Minecraft 1.12.2
Forge 14.23.5.2847

Impact 4.8.3 

OptiFine 1.12.2 HD U F5

 

When I'm only using Impact, it runs fine, game runs fine. 
When I'm only using Optifine, it runs fine, shader works, game runs fine. 

When I try to run both at same time, it hangs after it says 'Building Terrain.' (See attached screenshots.)

 

I know it's probably:

-A setting I'm missing.
-A line that needs to be added to a JSON or something.
-I have the wrong version of one of the files.

 

Any assistance would be appreciated. I can provide logs and any other required information. 

1.12 is no longer supported due to age.

Please update to a modern version (1.14.4/1.15.2) to receive support.

 

More information on supported versions can be found in the LTS link at the top of every page.

No longer supported meaning I can't ask for assistance here or it won't work?
I can't update from 1.12.2, that's what the server uses.

It is no longer supported here, you will have to look elsewhere for assistance if you must use an outdated version.

As for optifine/impact/whatever, no idea if those work, but I have recently (without support) run forge for 1.12.2 so I know that at the very least was working.

Gotcha. Thank you. Take care.