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.

When I've seen people make macarons in the past, they drop the tray onto the work surface once or twice (from a relatively low height) before they leave them to sit before going in the oven. If you haven't been doing this with yours you might want to try adding this step to your process as I believe it could help with your problems.

according to Adriano Zumbo the trick to thinning the mixture comes after you have folded all your sieved ingredients into your stiff peaked egg white: using an electric beater give the mixture a pulse to loosen it. Check it & pulse again if needed. It will only take a few pulses to loosen. The consistency you are trying to achieve is still very thick but will flow slowly off the beaters like lava. Also when you pipe the little peaks should point straight up to help the mixture flow to a smooth domed finish. After piping gently tap under the tray twice to help air bubble out. To achieve a smooth finish & feet they need to sit & dry out for 10-15 minutes on the bench before baking. There are some very detailed videos on the zumbobaking website. Although they are for his baking mixes the technique is exactly the same for macarons from scratch.

you probably need to sift your almond flour/confectioners sugar mixture after blitzing it in the food procesor, this ensures that you achieve the smooth domes you desire.