so im now editing moartinkers to try add support for compendium armours
added the stats, but it seems its not working.
i intend to do the same for conarm but not yet got to it due to running into this issue with compendium.

so this is how compendium registers its stats

TinkerRegistry.addMaterialStats(TinkerMaterials.endstone, new HelmMaterialStats(420, 3, 1, 0.4f));
TinkerRegistry.addMaterialStats(TinkerMaterials.endstone, new ChestMaterialStats(420, 6, 1, 0.8f));
TinkerRegistry.addMaterialStats(TinkerMaterials.endstone, new LegsMaterialStats(420, 5, 1, 0.6f));
TinkerRegistry.addMaterialStats(TinkerMaterials.endstone, new FeetMaterialStats(420, 3, 1, 0.2f));

so i checked HelmMaterialStats which is one of the 4 from compendium

    public HelmMaterialStats(int durability, int rating, int toughness, float potency) {
        super(durability, rating, toughness,potency, TYPE);
    }

went into MaterialRegistration in moartinkers and added this

    MaterialRegistrationBuilder setHelm(int durability, int rating, int toughness, float potency) {
        this.helm = new HelmMaterialStats(durability, rating, toughness, potency);
        return this;
    }

then i did the same for chest, legs and feet

updated the code that registers them in MaterialRegistration

        TinkerRegistry.addMaterialStats(material, head, handle, extra, bow, helm, chest, legs, feet);
        if (bowstring != null)
            TinkerRegistry.addMaterialStats(material, bowstring);

then i went into ModMaterials
added the new stats for each material
heres enderium for an example

private static MaterialRegistration[] materials = new MaterialRegistration[]{
        new MaterialRegistration.MaterialRegistrationBuilder()
                .setIdentifier("enderium").setColor(0x006E61).setTemp(1200)
                .setTraits(
                        new Tuple[]{
                                new Tuple<ITrait, String>(TinkerTraits.enderference, null),
                                new Tuple<ITrait, String>(ModTraits.enderMagnetic, MaterialTypes.HEAD)
                        })
                .setHead(1020, 8.31f, 10.19f, HarvestLevels.COBALT)
                .setHandle(0.42f, 600).setExtra(60)
                .setBow(1.22f, 1.1f, 5f)
                .setHelm(1020, 4, 2, 4)
                .setChest(1020, 6, 2, 4)
                .setLegs(1020, 5, 2, 4)
                .setFeet(1020, 3, 2, 4)
                .build(),

.setHelm .SetChest .setLegs .setFeet being the compendium stats

but sadly nothing happens

If you're simply trying to add new materials to the game or trying to add new parts to existing materials, may I suggest trying Armory Expansion? You should just need a single class to define what mods are required and what the files are named and everything else is done through JSON.

Example of an add-on's main class.

Example of the materials JSON.
Example of the ore dictionary JSON.
Example of the traits JSON.

Meanwhile, I'll try to look at this and get it fixed. I'll also mention that there are a couple of bugs with materials that need to be cast in Armory Expansion though.