Yes, I'm up to 6 floors now and am almost at the size limit for that area. I'm hoping to at least get all the floors furnished and powered before hitting the size limit. My first floor is fully furnished with a terminal, storage and safes, a pool table as a dinner table, a couple of nuka cola machines (note you have to use the grab function to put stuff in unless you make the ICE chest), seating, and two turrets watching the door. My second, third, fourth, and fifth floors are unfurnished, and I consider the actual gas station below technically as a basemant since I'm building on top, so a total of 6 floors. On my fourth floor, there are balconies on all corners for defense, and a walk way around the rocket ship on top of the gas station for outdoor patio furniture.
Later, I'm hoping to build a mini-Tenpenny tower at the drive-in theater if I find enough materials.
Since there are 30 total settlement areas, I am finding I am scrapping everything at those locations and taking them for use at my main locations. I may build a small pre-fab shack with some storage in them later on.
Just a few quick tips
-attackers will spawn anywhere inside your settlement, build defenses all around
-containers made are best kept to areas where settlers cannot normally reach
-take fusion cores out of unused power armor so they cannot be stolen.
-fence in generators and water purifiers so they cannot be damaged as easily
-build to your style, not what you think your settlers need
-if you want supply lines and stores, take the Local Leader perk.