How to make Mobs Follow R15 instead of R6 Characters?

I tried changing Torso to UpperTorso where it was needed, but that didn't seem to work. So how do I change that the Mob will Follow R15 Characters instead of R6?

local Module = require(Game.ServerScriptService.MobFunctions)

local larm = script.Parent:FindFirstChild("Left Arm")
local rarm = script.Parent:FindFirstChild("Right Arm")
local Debounce = false
local OrigPos = script.Parent.Torso.Position

LinkedSword = nil
TicksUntilWander = 0

script.Parent.Name = script.Parent.SETTINGS.MobName.Value .. " [" .. script.Parent.SETTINGS.Lvl.Value.. "]"
script.Parent.Human.Health = script.Parent.Human.MaxHealth

--Damage on hit.
function DamagePlayer(Hit)
    if Hit.Parent:FindFirstChild("Humanoid") ~= nil and script.Parent.Human.Health > 0 then
        if Debounce == false then
            Debounce = true
            Module.AttackPlayer(script.Parent, Hit.Parent:FindFirstChild("Humanoid"), script.Parent.SETTINGS.MinDmg.Value, script.Parent.SETTINGS.MaxDmg.Value, script.Parent.SETTINGS.HitChance.Value, script.Parent.SETTINGS.CritChance.Value, script.Parent.SETTINGS.CritMagnitude.Value)
            wait(script.Parent.SETTINGS.CooldownMagnitude.Value/100)
            Debounce = false
        --else print("Debouncing")
        end
    else 
        return false
    end
end 

function RegisterTool(tool)
    if tool:IsA("Tool") then
        LinkedSword = tool
        LinkedSword.Handle.Touched:connect(DamagePlayer)
    end
end

larm.Touched:connect(DamagePlayer)
rarm.Touched:connect(DamagePlayer)
script.Parent.ChildAdded:connect(RegisterTool)

--XP and Gold on death.
function Died()
local tag = script.Parent.Human:FindFirstChild("creator") 
    if tag ~= nil then 
        if tag.Value ~= nil then 
            local Leaderstats = tag.Value:FindFirstChild("leaderstats") 
            if script.Parent.SETTINGS:FindFirstChild("XP") ~= nil and script.Parent.SETTINGS:FindFirstChild("Gold") ~= nil then
                Module.AddStats(Leaderstats, script.Parent.SETTINGS.XP.Value, script.Parent.SETTINGS.Gold.Value)
            else 
                print("Can't find XP and Gold!")
            end
        end
    end
    if script.Parent:FindFirstChild("Model") ~= nil then
        if script.Parent.Model:FindFirstChild("Part") ~= nil then
            script.Parent.Model:Destroy()
        end
    end
end

script.Parent.Human.Died:connect(Died)

--Spawn initial part for purpose of returning. The purpose of this is to fix the wander as they move in straight line unintentionally.
if script.Parent:FindFirstChild("Model") == nil then
    model = Instance.new("Model", script.Parent)
    part = Instance.new("Part", model)
    part.Anchored = true
    part.CanCollide = false
    part.Transparency = 1
    part.Position = OrigPos 
end

--Follow
function findNearestTorso(pos)
    local list = Game.Workspace:GetChildren()
    local torso = nil
    local dist = script.Parent.SETTINGS.ChaseRange.Value
    local temp = nil
    local human = nil
    local temp2 = nil
    for x = 1, #list do
        temp2 = list[x]
        if (temp2.className == "Model") and (temp2 ~= script.Parent) then
            temp = temp2:FindFirstChild("Torso")
            human = temp2:FindFirstChild("Humanoid")
            if (temp ~= nil) and (human ~= nil) and (human.Health > 0) and (script.Parent.Torso.Position - OrigPos).magnitude <= script.Parent.SETTINGS.ChaseDistance.Value then
                if (temp.Position - pos).magnitude < dist then
                    torso = temp
                    dist = (temp.Position - pos).magnitude
                end
            end

        end
    end
    return torso
end

while true do
    wait(0.2)
    --Chase
    local target = findNearestTorso(script.Parent.Torso.Position)
    if target ~= nil then
        script.Parent.Human:MoveTo(target.Position, target)
    end
    --Wander
    if TicksUntilWander > 0 then
        TicksUntilWander = TicksUntilWander - 1
    else        
        TicksUntilWander = math.random(10, 25)
        if target == nil then
            if script.Parent:FindFirstChild("Model") ~= nil then
                script.Parent.Human:MoveTo(Vector3.new(OrigPos.X + math.random(-script.Parent.SETTINGS.WanderRadius.Value, script.Parent.SETTINGS.WanderRadius.Value), OrigPos.Y, OrigPos.Z + math.random(-script.Parent.SETTINGS.WanderRadius.Value, script.Parent.SETTINGS.WanderRadius.Value)), script.Parent.Model:FindFirstChild("Part"))
            end
        end
    end
end