I would sketch it out on paper and include dimensions. You can put your kettle on the burner stand and measure the height. That height will be the minimum level of the mash tun outlet (I would add a few inches for clearance and contingencies). Then, the top of the mash tun would be the minimum height for the outlet of your HLT (again, add a few inches for clearance etc). So, there you have the height of the three tiers. One thing you want to think about is how you will get the water into the elevated HLT and how you will be heating it. Any burners beneath the HLT or MT will increase the height. You will soon discover that the three tiers can wind up being quite tall. You will want to be able to see down into the mash tun and have easy access to it for stirring etc. This may require you to stand on a platform of some kind which is not real convenient. Consider buying a pump which will allow you to reduce the height of everything. I realize that a pump was not in your plans, but maybe reconsider that. Regarding space economy. Consider putting together a modular system. IOW, not a fixed stand, but individual components. I do it that way for just that reason. I built a wooden tower with top, middle and bottom platforms. The foot print is only 2 ft x 2 ft and much of my equipment, burners etc can be stored on the shelves. When in use, the HLT cooler is on the top. The middle shelf holds miscellaneous equipment and the bottom shelf is where I have the pump mounted on a movable base. I have two propane burners. One for the boil kettle and one for the mash tun. These are stand alone units. The burners and the pump are stored on the tower shelves when not in use and the HLT cooler stays on the top. I store the two kettles separately. So, I have basically a two tier setup as the MT and BK burners are on the floor and I pump to make the transfer. The sparge water is gravity flow. I simply fill the HLT with cold tap water with a hose and heat the water with a bucket heater. Hope this is of some help.