I do it cheated up a little from centered on the leg. Works out to about the same as sweetts. Sleeves I center.
My screens limit me to 13" on sleeves or legs.
As for how it reads, I do them the same as sleeves; right side top to bottom. left side bottom to top.
My reasoning on sleeves has alwasy been that one has their arms out in front way more than sticking backwards, and when they are out in front the text reads correctly from the side.
Stack the letters vertically, and you avoid the argument, but some fonts work better than others, and besides, in the end, it's up to your client. You just often need to give them your professional advice.
btw, when this came up in our last hang out, feathers flew and a debate ensued!
At any rate, that's my story, and my position, my orientation, and I'm sticking to it.