Spanning/centering elements with Grid/GraphicsGrid when there's a non-equal number of elem. in rows

Question

I'm trying to align elements in Grid/GraphicsGrid:

Grid[{{a,b,c},{d,e}}]

This makes d,e aligned to the very left of the bottom row. When I do

Grid[{{a,b,c},{d,SpanFromLeft,e}}]

only d is in a position where I want it. What to do to have e placed just next to d (or, in other words, between b and c)? Unfortunately, there is no SpanFromRight (why?).

Thanks in advance!

EDIT: I'm in fact interested in GraphicsGrid; I thought that Grid will be sufficient to convert it, but the plots look terrible (below) or are totally misaligned (when plaing with ImageSize, especially when I go to Grid[{{a,b,c,d},{e,f,g}}], where a,...,g are ListContourPlots with Legend:

EDIT2: The layout and formatting now seem to be perfect, but... Probably it should now be switched to Export problems. I have a nice looking output in MMA, but after Export to .eps I get this result (placings should be as shown above) (converted to from .eps output to .jpg 'cause size limit):

Answer 1

Maybe

Column[Row[#, Spacer[5]] & /@ {{a, b, c}, {d, e}},  Alignment -> Center]

{a, b, c, d, e, f, g, h, i} = 
  Table[With[{data = MapIndexed[Flatten[{##}] &, RandomReal[1, {100, 2}]], 
     color = RandomChoice[ColorData["Gradients"]], 
     intord = RandomInteger[{0, 4}]}, 
    ListDensityPlot[data, InterpolationOrder -> intord, ColorFunction -> color,
     Mesh -> All, ImageSize -> 200, ImagePadding -> {{20, 5}, {20, 5}}, 
     PlotLegends -> BarLegend[Automatic, LegendMarkerSize -> 200]]], {9}];

Column[Row[#, Spacer[5]] & /@ {{a, b, c, d}, {e, f, g}, {h, i}}, Alignment -> Center]

Answer 2

Well, what you want is not really a simple grid, because its irregular, but a combination of two grids:

Grid[{{Grid[{{a, b, c}}]}, {Grid[{{d, e}}]}}]

The other thing you can try is to construct it by rows and columns:

Column[{Row[{a, b, c}, " "], Row[{d, e}, " "]}, Center]

Here's nice overview of all this stuff:

https://reference.wolfram.com/language/tutorial/GridsRowsAndColumns.html