J, I found a recipe for a 10 inch Bolognese Rice cake so doubling your version is fine.
While reading the recipe I was kind of startled to realize I just made something like it yesterday--only mine was baked rice pudding.
Seriously. Who knew they could be so close and yet so different.
Here's what I used:
1 half gallon milk (8 cups)
2 cups Arborio rice
6 eggs
1 cup of golden raisins
1 stick of butter
3/4 C sugar
1 tsp vanilla
lemon zest
cinnamon
This recipe cooks the rice/milk/butter stovetop for 75 minutes (stirring a LOT) until very thick. Then the eggs are beaten with the sugar and spices, tempered with hot rice and added to the rest of the rice.
I thought it was a little runny, so I buttered a deep Pyrex casserole and baked it off for 45 minutes at 350. Mine was 2.5" thick and the very center is still moist today, while the edges are firm enough to slice.
Your doubled version should work fine. But...if it looks too jiggily in the middle, just tell them it's rice pudding cake.
Odd little note: The Arborio rice cost $6.95 for a 2 lb canister. I was actually looking for Valencia short grain starchy rice which is only $0.99 for a 1 lb bag and cooks up very creamy for rice pudding. But I couldn't find it anywhere in Ingles. Odd, because I could always find it in FL.
http://www.geniuskitchen.com/recipe/bolognese-rice-cake-340819