The advantages of threaded rods increases as the size of the tissue poured increases. A 20 inch rod is convenient for A3 or slightly larger pours. A 40 inch is a little harder to use uniformly but still makes large tissue pours really easy. A 12 inch rod may not be all that useful next to any other method of pouring, such as spreading with a comb or with hands, except they help to disperse bubbles quite well. Wasting a little glop is really no problem, you can just scrape it up and reuse it anyway. I use a 20 inch and a 40 inch RD200 with 12.5% gel for tissue and a 20 inch RD95 with 10% gel for sizing paper, only because those were the sizes in the group order that happened last year. The 40 inch allows me to effectivly pour 4 A3 sheets in 1 pour, a great time saver, and the smaller rod makes it easy to pour smaller sheets each with different tones or colours. A fairly coarse threaded rod should work fine as CMB suggests. Some people seem to prefer a hollow hot water filled pipe with magnetic strips to hold it up, that works ok too. Overall though, a threaded rod seems to be best at ferreting out the air bubbles and the simplest clean up.