[yj589794]

For that I think you'd have to generate headers for the <25 raid and >25 raid separately:

local toStr = tostring

local function spawnFunction(self)
	self:SetActiveStyle('oUF_EPRaid')

	-- define the raid groups
	local raid25 = {}
	for group = 1, NUM_RAID_GROUPS do
		local header = self:SpawnHeader(nil, nil, 'custom [@raid26,exists] hide;show',
						'showPlayer', true,
						'showParty', true,
						'showRaid', true,
						'groupFilter', toStr(group),
						'yOffset', -config.SPACING,
						'oUF-initialConfigFunction', ([[
							local unit = ...
							self:SetWidth(%d)
							self:SetHeight(%d)
						]]):format(config.RAIDUNITWIDTH, config.UNITHEIGHT)
		)

		if group > 1 then
			header:SetPoint('TOPLEFT', raid25[group - 1], 'TOPRIGHT', config.SPACING, 0)
		else
			header:SetPoint('TOPLEFT', UIParent, 'BOTTOMLEFT', 15, 350)
		end
		raid25[group] = header
	end

	local raid40 = {}
	for group = 1, NUM_RAID_GROUPS do
		local header = self:SpawnHeader(nil, nil, 'custom [@raid26,exists] show;hide',
						'showPlayer', true,
						'showParty', true,
						'showRaid', true,
						'groupFilter', toStr(group),
						'yOffset', -config.SPACING,
						'oUF-initialConfigFunction', ([[
							local unit = ...
							self:SetWidth(%d)
							self:SetHeight(%d)
						]]):format(config.RAIDUNITWIDTH, config.UNITHEIGHT)
		)

		if group > 1 then
			header:SetPoint('TOPLEFT', raid40[group - 1], 'TOPRIGHT', config.SPACING, 0)
		else
			header:SetPoint('TOPLEFT', UIParent, 'BOTTOMLEFT', 15, 350)
		end
		raid40[group] = header
	end
end

I don't use the visibility settings much, but the above *might* work