Lag issues: Changing Startup parameters?

[BossX]

My modpack is pretty laggy, so I decided I wanted to install the FPSPlus mod. To do this, I have to change the startup parameters. Only issue, I have no idea how to do this.

 

I have to add these flags:

-Dfml.ignoreInvalidMinecraftCertificates=true -Dfml.ignorePatchDiscrepancies=true

[plowmanplow]

There is a file in the modpack.jar file named "version.json". In that file you can see other java arguments at the top. You can extract that file, add those arguments, and put the file back in the archive (rename it to modpack.jar.zip first). You might also try OptiFine and fiddle with the options there. It helps some, does nothing for others, and total fails with some. Your mileage may vary.

[BossX]

I've tried using Optifine (I'll try again), but it didn't load correctly. So I'm going to try FPSPlus as an alternative.