Config Issues, Working in Eclipse, not once compiled [1.11.2]

Hi, I have IFuelHandler implemented as an Inferface so I can have fuel handlers individually enabled/disabled rather than having to put each fuel in its own class. I know I could use a map to do this as well, but I'm quite frankly not super knowledgeable about maps in Java or any language. In eclipse, my code works. When i run the project, the fuel handlers work, and when i edit the config file stored in the run directory, I can disable them. However, when I compile this into a mod using the "gradlew build" command, the resulting product has the same code (checked sources.jar) and outputs the config file correctly, but the fuels do NOT work at all and the config switches seem to be dead weight. Of note, I had to change source-compatibility in build.gradle from 1.6 to 1.8 so it would compile correctly as java 1.6 and 1.7 don't allow use of Lambda expressions. Here is my code:

NewFuelSystem.java

package com.bored.morefuelsmod.newfuelsystem;

import net.minecraft.init.Items;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraftforge.fml.common.IFuelHandler;
import net.minecraftforge.fml.common.Optional.Interface;

public class TestFuelSystem{
	public static IFuelHandler arrow = s -> {
		  if(s.getItem() == Items.ARROW){
		    return 100;
		  }else{
			  return 0;
		  }
		};
	public static IFuelHandler apple = s -> {
		if(s.getItem() == Items.APPLE){
			return 100;
		}else{
			return 0;
		}
	};	
}

Main.java (excerpt)

@Mod.EventHandler
	public void preInit(FMLPreInitializationEvent event){
//Skip unrelated code
Configuration config = new Configuration(event.getSuggestedConfigurationFile());
		config.load();
//Skip unrelated code
boolean enableTest1 = config.get(Configuration.CATEGORY_GENERAL, "fuelenableTestExperiment1", true).getBoolean(true);
			if(enableTest1)
				GameRegistry.registerFuelHandler(TestFuelSystem.arrow);
		boolean enableTest2 = config.get(Configuration.CATEGORY_GENERAL, "fuelenableTestExperiment2", true).getBoolean(true);
			if(enableTest2)
				GameRegistry.registerFuelHandler(TestFuelSystem.apple);
//Skip unrelated code
config.save();
}