Interstage not shielding engine properly

[R_Skoklater]

Hello I made an interstage mod with a decoupler node that pushes the engine outside the interstage. The interstage itself is hollow (including the colliders "COLInterstage" ) but has caps (top and bottom caps) that are not hollow to enclose the interstage. The caps are set to convex and trigger so that the upper stage can decouple and separate from it without explosion.

My issue though is this. And for three days nonstop I tried everything I could learn on the old wiki and searching forums but nothing solved my problem.
The ModuleCargoBay doesn't seem to work. Normally if it's shielding the engine, the engine's drag value should be 0.00 but it's still interacting with the airflow outside.

Here is the config file:

PART
{
    name = Frustrum_Interstage
    module = Part
    author = SkyRock Corp.
    MODEL
    {
        model = SkyRockCorp/Interstage/Interstage
    }
    rescaleFactor = 1.0
    node_stack_top2 = 0.0, 0.998, 0.0, 0.0, -1.0, 0.0, 2
    node_stack_bottom2 = 0.0, -2.04, 0.0, 0.0, 1.0, 0.0, 2

    node_stack_top = 0.0, 1.141, 0.0, 0.0, 1.0, 0.0, 2
    node_stack_bottom = 0.0, -2.163, 0.0, 0.0, -1.0, 0.0, 2

    node_stack_top3 = 0.0, 1.141, 0.0, -1.0, 0.0, 0.0, 2
    node_stack_top4 = 0.0, 1.141, 0.0, 1.0, 0.0, 0.0, 2
    TechRequired = generalConstruction
    entryCost = 2200
    cost = 2800
    category = Coupling
    subcategory = 0
    title = Interstage Adapter 2.5m to 3m
    manufacturer = SkyRock Corp.
    description = This Adapter houses the upper stage engine/s (Currently supports the Cheetah engine only!) and separates the stages and payload fairings. The fairing supports up to 3.8 meters high payloads and 3.2 meters wide payloads.
    attachRules = 1,1,1,1,1
    mass = 1.85
    dragModelType = default
    maximum_drag = 0.2
    minimum_drag = 0.3
    angularDrag = 0.2
    crashTolerance = 6
    breakingForce = 200
    breakingTorque = 200
    maxTemp = 2000 // = 3000
    fuelCrossFeed = False
    stageOffset = 1
    childStageOffset = 1
    inverseStageCarryover = false
    bulkheadProfiles = size2
    tags = #autoLOC_500174
    fx_gasBurst_white = 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, decouple
    sound_decoupler_fire = decouple
    
    MODULE
    {
        name = ModuleDecouple
        ejectionForce = 250
        isOmniDecoupler = false
        explosiveNodeID = bottom3        
    }
    
    MODULE
    {
        name = ModuleServiceModule
        ExteriorColliderName = COLInterstage
        ShellMeshName = COLInterstage
        partDecoupled = false
    }

    MODULE
    {
        name = ModuleCargoBay
        DeployModuleIndex = 0
        closedPosition = 0
        lookupRadius = 1.0
        useBayContainer = true
        bayContainerName = COLInterstage

        nodeOuterForeID = top
        nodeOuterAftID = bottom
        nodeInnerForeID = top2
        nodeInnerAftID = bottom2                  
    }
    DRAG_CUBE
    {
        cube = Default, 8.675,0.2549,1.701, 8.675,0.2553,1.701, 7.748,1,0.09618, 7.748,0.7187,3.407, 8.675,0.2549,1.701, 8.675,0.2553,1.701, -3.052E-07,-0.511,7.629E-07, 3.216,3.304,3.216
    }
}
}
 

Here are some images of the interstage and the hierarchy in Unity. (I separated the colliders that way I can achieve a hollow center)