I've heard of Ipe but I've never seen any to my knowledge but Kumaru is a complete new one to me. It does sound OK, is it stable? That's the most important thing to me, I will live with non oily woods (they can be sealed) but stability is paramount.
Other than Teak I quite like Sapele for gun making. It's reasonably dent resistant, stable and as long as it's well sealed it is as good as anything else with the added bonus that it costs next to nothing. The lightweight woods (less dense) have the advantage of allowing you to be more flexible in the way you ballast the gun E>G> a mid handled gun with a heavy shaft could be balanced by putting more lead at the back of the gun. Try that with a dense wood and you would either have to put up with a sinker of a gun or have it permanently nose heavy.
Check out Scott Merlo's info on woods
woods