Not every flute or mechanism is the right size/shape for every hand/body.
On my main flute (the Nagahara Full Concert) I have one permanent modification and a couple that I add now and then:
After using a plastic "C# key extension" made by Brannen for about an entire year (and having to replace them all the time - at $40 a pop! - because they were made to fit Brannen and not Nagahara) I was still unsure if I wanted to make a permanent change to my flute so I asked my local flute repair wonder-woman Lori Lee to make me a removable but more sturdy metal extension. Lori's contraption worked very well for a while but I finally decided to make a permanent change. I requested a different C# key shape from Nagahara and they were able to replace the old C# very easily. I must not have been the only person to request this modification. The price of the key replacement was LESS than what I spent on replacing the plastic Brannen extensions! In the future, I would make my own temporary C# key extension out of buttons (see below for photos) and save some $ while I decide whether I need to make it permanent.
I found that my high register technique and comfort in my left hand improves a lot when I can bulk up the tube where my left hand touches the flute body. I made a left hand index finger/hand rest by pulling rubbery pencil grips off some mechanical pencils and cutting them lengthwise. The beauty with this material is that it keeps its shape and will fit on a C flute without leaving any marks on the silver. I usually put a piece of masking or painters tape on top of it because the rubber is too tacky sometimes. Some people use a piece of adhesive moleskin padding instead and that works well too but I found that I needed to replace it much more often because it will eventually fall apart or get dirty. On my Sankyo Kingma system flute, I use a piece of plastic flexible tubing I bought from the hardware store instead (see additional photos below).
In my right hand, I usually place a cork plug in my E key because my ring finger naturally wants to drift closer to my middle finger and I have to make an extra effort to cover the hole otherwise.
Experiments with my new Sankyo Kingma System flute:
I use the same plastic tubing on alto and bass flutes but it's not to bulk up the left hand area, it's just for a bit better traction. On these larger instruments, I also use a piece of adhesive moleskin pad where my right thumb touches the flute for comfort.
For some flutists, an offset G is not the ideal setup. I told myself that I would go back to an inline G on my next flute. But my next flute ended up being a Kingma System Sankyo so an inline G is not possible.
There is no hard and fast rule about who should have an inline or offset G. Some say that the off-set G is more ergonomic - it might be more ergonomic for some people, but NOT EVERYONE. Those with short fingers should give a flute with an inline G a serious audition (over several days) with fast technical passages in the high register. I've seen/heard those with really long fingers play very well on inline and offset G flutes. I've also seen/heard those with short fingers play very well on both types. Play the flute that works best for you, keep an open mind/ear, and stay aware of your body so that when your hands give you hints that something is not working well, you can make the necessary changes.
One reason that some (especially flute repair pros) might favor the offset G: it's easier to maintain and work on since there's less going on in the main rod. Because of this, I think it's probably easier to manufacture student model flutes with the offset G. I'm speculating that this is why most new student model flutes are offset these days, not because it's more ergonomic than inline G flutes. If anyone has a good explanation other than it's more ergonomic (because I do not buy that reasoning) please let me know!
If I did not play so much contemporary music, I would get a closed-hole or plateau style flute - in which case, it's not as important whether the flute in in-line or offset.