I just finished making a 3D pumpkin cake using 2 "sphere"-like halves. I sandwiched a cookie in between with BC and then did my crust layer in BC. My question is how do you then cover a round object in fondant/RBC? I used RBC and had a difficult time covering the bottom half of the sphere. Would it have been better if I covered each half separately and then assembled the cake? Any tips?
In my experience (which some would argue is limited...) I find that you will have to cut some fondant off when covering the bottom half. I'd try to make the seam fall in the indent of the pumpkin if you can, so it can be in the shadow.
I don't think covering the halves separately would help....the bottom one would peel off and fall, from the "equator" down. Or at least could. I think it's a matter of luck.
If you can use modeling chocolate instead, I find it easier to blend seams with that rather than fondant. I have no experience with RBC so I can't answer for that.
I love RBC for spherical cakes because it's self-healing and doesn't "pleat". I conver the whole thing with a large piece of RBC and gently press toward the bottom. I cut off the excess and use the heat of my hand to mold it to the shape. I buff it with some PS and/or CS on my hands.
here are different posts discussing this: