here is the problem putting more hot soil in the bottom. the roots wont grow into the hot soil. they stop. they eat what they need then and only then grow deeper. so, if you do 1/3, they have more room to grow big enough to want to eat the hot soil nutes and grow deeper. if you use 50% they only have the other 50% to get big enough to eat the nutes and go deeper - roots need to grow downward to grow green upwards. if they only grow a little down they only grow a little up. the other thing is no matter what you put, they use only what they need, so you have lots of the pot the roots wont use ever due to it being hot and they only need so much hot nute filled stuff. so wasted resources and taking away grow room are the two good reasons to stick to the 1/3.
i cant share the articles because they are college library stuff, sorry. but google some canada or washington state stuff on it. they are doing some actual peer reviewed research on the growing.