[Dawn]

I'm currently spawning maintank (and maintank target via xml template) and boss frames like this

	self:SetActiveStyle"Nivea - Boss"
	local boss = {}
		for i = 1, MAX_BOSS_FRAMES do
			local unit = self:Spawn("boss"..i, "oUF_NiveaBoss"..i)

			if i==1 then
				unit:SetPoint("CENTER", 400, 200)
			else
				unit:SetPoint("TOPLEFT", boss[i-1], "BOTTOMLEFT", 0, -10)
			end
			boss[i] = unit
		end
		
	self:SetActiveStyle"Nivea - MainTank"
	local Main_Tank = self:SpawnHeader("oUF_MainTank", nil, 'raid,party,solo', 
		'showRaid', true, 
		"groupFilter", "MAINTANK", 
		'yOffset', -20, 
		"template", "oUF_NiveaMTartemplate"
	)
	Main_Tank:SetPoint("TOP", UIParent, "TOP", 540, -280)

and I adress them via

local UnitSpecific = {
	boss = function(self)
		Shared(self)
		
		self.Power:SetWidth(Ncfgfs.width.M)			
		self:SetAttribute('initial-height', Ncfgfs.height.M)
		self:SetAttribute('initial-width', Ncfgfs.width.M)		
	end,
	
	MainTank = function(self)
		Shared(self)
		
		self.Power:SetWidth(Ncfgfs.width.M)			
		self:SetAttribute('initial-height', Ncfgfs.height.M)
		self:SetAttribute('initial-width', Ncfgfs.width.M)		
	end,	
		
}

I don't know if that's a good way, but it works. I'll have to look into arena frames, later.