I can think of no one else better acquainted with mantis anatomy, so I'm curious: What ratio of man to mantis do you like in an anthro mantis race like D&D's Thri-Kreen? 5e's PC rules only stipulate a bipedal stance with two sets of arms, the lower pair being a bit smaller. Official art doesn't give them abdomens anymore, but that's where their guts are! How would you roughly imagine their body plan without sacrificing insectoid aesthetics or humanoid player character function?
Honestly, mantises as is are already amazingly humanoid. They even have little two-clawed "hands" (tarsi) that unfold from the sides of their raptorial claws! Just make those "finger" claws a little bigger and more dextrous, add some thumbs, and voila! Insect centaur.
