A few links you should consider checking out today.
Should you be trying to release your psoas?
This blog was new to me and I believe I found it via the Facespace. Anyway it's a great discussion about the merits of attempting to release the psoas. I've personally used this practice myself and it's not fun at all. Adam puts forth some compelling reasoning to perhaps forego the practice, which I wouldn't be too upset about personally.
Tony's blog. It's all good.
I've had to recreate this post because for some reason the orginal was lost or deleted. I do know that I referenced Tony Gentilcore's blog, but I can't exactly remember the post. It doesn't matter though as I usually like just about everything Tony ever posts. Go check out his blog.
Breathing during the overhead press might be what's holding you back from bigger presses or extra volume overhead. This is an old article I wrote about setting up your breathing for the overhead press. I'm working on adding some new thoughts on this in a newer post but in the meantime the original still hammers home a point about breathing to maximize the press.