Vanilla sponge cake for carving

I need a good sponge cake recipe for carving a car cake. My husbands uncle Mike is having his 70 th birthday. I am doing a practice carve. My first car was too crumbly and didn't have a nice shape.
I doubled this recipe
Instructions
2c cake flour( I used all purpose and three tsp of baking powder)
0ne cub butter to melt
1tbsp vanilla
1 1/4 c sugar
5 large eggs
5 large eggs yolks
Preheat oven to 375. Spray two  8 or 9 in round cake pans or line bottom with parchment paper
Sift flour twice and set aside
Melt butter in saucepan over low add vanilla after removing from heat
Combine eggs yolks and sugar in metal bowl place over simmering water on stove Wisk constantly. Until warm to touch or candy thermometer reads 120 degrees
Remove bowl and attatch whisk to mixer  whip egg mixture on medium until foam triples in volume and begins to recede 5 min stabilize on low speed for 10 min.
Fold in flour using spatula. Blend small amount of batter into melted buyer then fold tempered butter into mixture.
Fill in prepared cake pan bake until firm to touch about 30 min cup cakes 20 min.
Kart cool in pan a few min before turning to wire rack can we wrapped and stored for two days or frozen for three weeks
Wow this batter is so fluffy like marshmellows! Hope it carves well!
I baked it in a 13 by 9 inch pan for my rectangle shape of a car after 30 min its still jelloy so I'm adding ten more min.
may 4th 2013 im making again doubled recipe 70 degree weather my fondant is bubbling :(

This is the tempered melted butter with some batter whisked in.
baking in a 13 by 9 in pan needs longer than 30 min
 Simmering water underneath this metal bowl of sugar and eggs combined.




This is how the batter looks after its folded the butter in.