Hey, I have had my veileds for a couple of years now. One male and one female. Each is in their own 24"x24"x36" screen cage. As far as I can tell, this is big enough for them. Them seem happy. I have it very well planted. They never climb on the screen or anything. I made the cages myself, they work great. I used regular screen, and not metal screen, HUGE MISTAKE. Easily avoidable, use the metal screen. Otherwise the crickets eat right through and it starts looking ugly fast. Anyhow, yeah, I think that cage dimensions you said are good. Bigger is always better, but I think it works. Every cham that you end up getting absolutely needs to live separately. They absolutely have to have the UV lights and trhey need calcium dusted crickets. You probably already knew all that, but I am just repeating it.
I have bred mine, everything went right according to plan. It was relatively easy, just the egss took 6 months to hatch, which is normnal, just tests your patience. Anyhow, good luck with it. Veileds are awesome. Don't forget though that they don't like to be handled (although I'm sure some people will disagree there). Anyhow, that's all I got to say. Good luck with them.
Chris Fullmer