How to make banana bread to bake through?
I periodically make banana bread, basically replacing water in bread with blendered banas and adding spices. http://delightsbites.blogspot.com/2011/02/best-banana-bread.html 
I usually add much more flour compared to what recipe calls for (they call for 4 bananas + 2 cups flour), but the dough tends to be very moisturous even after adding more flower.
Challenge is that if the dough is a bit too moisturous or the loaf is too large (I multiply all ingredients by 2), it doesn't bake through in 45 minutes @ 350F. Liquid dough stays inside. Yesterday I tried to bake larger loaf, and even though I added a lot more flour it didn't bake through just because of the larger size.
How to solve this problem that larger loaf doesn't bake through?