I have tried several times to do large stand up numbers on top of a cake with mixed results... I've tried cookies but those broke, the last few times I tried rolled gumpaste, cut out, but the surface is always wrinkly, and I still have trouble with them breaking when I handle to insert into the cake. Last night I made gumpaste numbers with skewers for a cake for this weekend... again with the wrinkles. My idea is to use them but attach a MMF cut out the same shape to the front. Do you think this will work? What should I use to "glue" the MMF to the gumpaste?
A few suggestions
The dowel you are using is much too large. Use the kind that is cheap, used for shish kebab on the grill. Amazon sells them in many lengths. I get the 6"
You are correct to cut 2 of the same letter or number. Let them dry for quite a while. The skewer will go between them, not into them. Once they are dry, you can use chocolate melts or royal icing to secure them to the skewer. If you want one solid number or letter, then make it much thicker.
The thin skewer is the trick.
Also, you only need a few inches to stick into your tier.
Make sure to allow them to dry on wax paper so they have no grab to the surface.