I've seen all these lovely pumpkin cakes and I can't imagine that you would give someone an 8 inch high slice of cake. Do you cut the top half off and move it over and then serve it as 2 cakes?
I always use a cake circle between the layers with a few straws for supporting the top layer. So, it's basically like cutting a bundt cake.....twice.
I made one for the first time a few weeks ago, so I can only tell you what I did. I made a large pumpkin and 3 smaller ones. The smaller ones were two of the small bundts frosted together and I cut those all the way thru.
For the large one, I frosted them together with no board in between. When I cut it, I could easily tell where the cake ended and the middle frosting started, so I just gave them a good sized slice of the top cake. We finished up the top and then cut the bottom cake. There was plenty of icing so there were no issues with that.
Again, this was just my experience. Others may know a better way.
I made a pumpkin for my little cousin's birthday a few weeks ago. The top cake was yellow cake and the bottom was chocolate, with a layer of chocolate icing in between. So I did cut the pumpkin in tall, skinny slices. No one complained and I thought it looked kinda cool with the contrast in colors 
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