I built twin swords with steel and Im on my 3rd pair now. The 1st ones were really bloody heavy and the tsuba was too small so I kept burning my hands, But they were great fun, when you have that sort of weight using 2 of them you can throw them around and use the other one as a counterbalance... tricky but effective.
The 2nd ones where very similar but a thinner sheet of steel was used and I knocked a few inches off the length, these were much easier to use but after a few burns they started to bend with the heat, annoying, had to be scrapped.
The 3rd pair were the original thickness but the same length as the 2nd ones. I got a larger tsuba put on to protect my hands and a pommel put at the very end of the sword as a counterweight which was also a really handy addition to the grip as I could throw them around alot quicker with no fear of thm slipping from my grip.
Now the warning... Playing with that sort of weight properly knackered my wrists and shoulders and I could only manage 2 mins before I got injured, I was forever seeing a Physio to get my shoulders sorted. Go light is my advice.