Overlapping NineSlice textures with ButtonFrameTemplate

[LudiusMaximus]

I am using ButtonFrameTemplate for a frame.
But as my frame has a low height I get overlapping NineSlice textures resulting in the frame shaddows adding up.

local myFrame = CreateFrame("Frame", "myFrame", UIparent, "ButtonFrameTemplate")
myFrame:SetPoint("TOPLEFT")
ButtonFrameTemplate_HidePortrait(myFrame)
myFrame:SetFrameStrata("HIGH")
myFrame:SetWidth(430)
myFrame:SetHeight(220)
 
myFrame.NineSlice.LeftEdge:Hide()
myFrame.NineSlice.RightEdge:Hide()

As you can see, I already removed NineSlice.LeftEdge and NineSlice.RightEdge but is it possible to crop the NineSlice corner textures somehow?

Or is there another solution like using the templates differently?