I have always done only two layers per tier, but lately some of my stacked cakes look a little "squatty" and short. Speaking about 2 inch layers, do you use two or three layers?

I use two two inch tall cakes and torte them both, giving me 4 one inch layers of cake. When you put in three layers of filling and ice it the cake is usually 4.5 or so in tall.

It depends on the look I am going for. I've done 2 layers and I've done 7 layers of cake. Usually, I would torte my two 2 inch cake so I get four layers.

No matter how many layers you use, the industry standard for a tier is about 4 inches. If you do larger tiers (i.e. 6 inches), be aware of what size plates the cake is being served on. A 6" slice of cake on a 6" plate can look messy, with potential overhang.

Thanks. I guess I've been a little scared of torting because I don't want the cake to slide on the filling (when it's hot outside). Any advice there?

If torting, reduce the amount of filling between each layer. Smaller layers of cake ... smaller amt of filling.