I would say thats an okay size for a female but a little to small for a male. It would also me okay for a young male but the cage would need to be upgraded for an adult one.
Is Yemen too big? Lol. The bigger your enclosure the more option you can provide for your Cham, from heat, uvb and humidity gradients, the more options the more your chameleon can self regulate. It's more comfortable and more natural that way
LOL...I've always wonder what are the scientific bases for the 2'X2'X4' recommended cage dimension, but could never find one. I'm beginning to think it was based on the size of Reptibreeze cages commonly sold in pet stores .