To solve the problem with the nuts sinking to the bottom of the cake you need to substitute the oil with Crisco Shortening (don't melt it ) and mix the batter longer so it will be very thick and fluffy. Don't add the chopped nuts until just before putting it in your pan.
Mix in the nuts with a wooden spoon . This should do the trick as oil makes your cake batter thinner and allows anything heavy to sink.
