Good dimensions for it , what body works best with.?
I wasn’t aware anyone was using brass tongues. Usually just the barrel is brass, with a wood or cane tongue. Where did you hear of brass tongues?
djm
I think there was a time when there was some experimentation with brass tongues among Northumbrian pipers.
There are double-reeds for regs made of brass or bronze. Perhaps you were thinking of these? I have only been muddling with these so far, but have found that I can’t use the same slip dimensions as for cane reg reeds. It is hard to get them up to pitch, as they want to play much lower if made to the same size as cane reg reeds. I am experimetning with .045" brass shim stock. So far, I have found that I can get them in pitch if I wind them twice as far up the reed blades as with cane, but then they don’t sound too good. Something to play with on a rainy day …
djm
Brass tongues can be problematic. In addition to sounding ‘brassy’ (harsh) Northumbrian piper’s found that verdigris is a problem.
You could always try the “French Method” 
Basically, this type of reed (drone) uses a brass body but the flat part where the reed tongue sits is covered with a very fine piece of leather with a slot cut in to match that of the slot or hole in the brass body. The advantage is twofold. The brassy sound is reduced and the veridgris also. This was explained to me by Colin Ross of the NSP Society.
Joseph (the UK one) 
I have made a few different versions of brass body/brass tongue drone reeds. In my Roberts drones they were quiet with an electronic organ sound. They also sounded more of a “pure” tone. I am not a expert, but they sound like they are playing closer to a single wavelength than a wood, cane, or plastic tongue. I liked the sound, but I was/am on a quest for buzzier drones.
I just think it is cool when the drones and the chanter are all vibrating together. It’s a much richer sound from where I sit, I don’t know if it sounds different to people sitting 5 feet away.