change the 'G limit' for F18

That is parameter which is defined in the TMD file in the flight controller for the F18. In the F15 this maximum acceleration limit is set higher, so copy paste from there.

The controls.tmd just changes the clickspots and has no physical impact whatsoever. The red error box is usually associated with a error message in the TM.log file. Make sure that you didn't accidentally change the syntax of the file.

This is the TM.log of a content converter which you don't need. No I meant the TM.log file of the simulator after the red error box was shown.

There are a ton of error messages from user scenery located in a Aerofly FS 2 folder, which makes it hard for me to see the issue with the aircraft. Please load the F15 first and then the F18 and then check the log file.

It looks like you accidentally added a > bracket somewhere which causes the file to not be loaded properly. Please restore the default file from your backup. If you don't have a backup you need to check the file integrity in Steam which may take a while.

Then make sure to only copy across the one single text line from the F15 flight controller to the F18 flight controller. It's literally a single line of code to change the max acceleration. Make sure not to remove or add any of the [, ], <, or > characters because otherwise the file syntax is broken.

Awesome, glad we got it working!