How can I make the tops of my macarons smooth?
The meringue should be glossy and form soft peaks. When you take your whisk out of the meringue it should look like this:





The French say that when you take the whisk out of the meringue, it has to look a bit like a bird's beak, hence the way the meringue forms a soft peak slightly pointing downwards.

But to be honest, I don't believe that is you problem. I guess you just undermix your batter. People often say it has to fall like a ribbon or like magma, but I always thought that is hard to imagine. You can take a knife and cut through the batter. If it flows back immediately, it's ready. But let me tell you: One or two strokes too much with the spatula and the batter becomes unusable.

And one tip I can give you: The process of transferring the batter into the piping bag also 'mixes' the batter, so maybe don't go too far if you are unsure.

And as already said, it is important to tap the the tray from the bottom after piping as it helps to remove any air bubbles in there. Also, always pipe straight from the top (90° angle). This also helps the batter to smooth out.

I wouldn't recommend you to chance the amount of powdered sugar, as the French use Tant pour Tant (TPT) for their macarons, which means fine almond meal and powdered sugar are mixed proportional to each other.

When mixed perfect, it looks like this:

http://1.bp.blogspot.com/_WhPHUKwckUw/S4WP1eBE7pI/AAAAAAAAB00/gYqFjGOvEiU/s1600-h/5.jpg 

When gone too far, it looks like this:

http://3.bp.blogspot.com/_WhPHUKwckUw/S4WP-q8RrdI/AAAAAAAAB08/7R6uO1uGfBQ/s1600-h/6.jpg 

Maybe try counting your strokes while mixing, some people say that it helped them.