[Phanx]

I don't know about Beautycase, but here is the code I use to add borders to Grid in my UI; since Neal based Beautycase on the border code I posted years ago anyway, it shouldn't be too hard to modify it:

local function noop() end

local function Grid_SetBackdropBorderColor(f, r, g, b, a)
	if a and a == 0 then
		f:SetBorderColor()
	else
		f:SetBorderColor(r, g, b)
	end
end

local function Grid_AddBorder(f)
	if not f.SetBorderColor then
		f:SetBorderSize(0.1)
		PhanxBorder.AddBorder(f)
		f.SetBackdropBorderColor = Grid_SetBackdropBorderColor
		f.SetBorderSize = noop
	end
end

for frame in pairs(GridFrame.registeredFrames) do
	Grid_AddBorder(_G[frame])
end

local o = GridFrame.RegisterFrame
GridFrame.RegisterFrame = function(self, f)
	o(self, f)
	Grid_AddBorder(f)
end

The "PhanxBorder.AddBorder(f)" line is the one you would need to change to call the Beautycase function that adds a border to a frame.