Well, no fears. If the front is too short, it will ride down with wear... And if it's too long, then of course it will ride up with wear...
The second part of your statement is correct. The first part however is
way off.
If your jacket starts out too short, it will only get worse with wear.
As leather developes creases and wrinkles, it will get shorter. Just look
at the sleeves as an example. The more your arms move, and the leather
gets creases and wrinkles in it, the shorter the sleeves will get.
The extra inch is usually added because as stated, if you measure from
the tops of your shoulders down your back to your waist, that measurement
is going to be shorter than if you measure from the tops of your shoulders
down your chest to your waist. This measurement is usually about 1
inch different on average. It will be even a greater difference for women
for obvious reasons.
If you check out some of the pictures posted to the main site, you can
see the people who did not add this extra inch have the jacket riding up
somewhat, while those who added it, have the front of their jackets almost
dead even with the back while they are wearing it.
Wested, and most other jacket makers make their jacket patterns with
the front and back panels the same length from the top of the shoulders.
I have added this extra inch to every leather jacket I have ever had,
and that includes a Wested Raiders, my Aero Californian, my Aero B-3
and a few A-2 jackets and a Real McCoys B-6.
And each time, they fit, look, and function much better, and don't look
like cheap mall jackets that ride up in the front.
But the front will never get longer with wear. It will only get shorter and
make the situation worse.
The best way to prove this to yourself is to have someone take a picture
of you, wearing your jacket, standing up straight, from the side. If you
just stand in front of the mirror and look at yourself, you do not get a real
view of how you look to others. If you have a digital camera, use the
auto function, and set it up so you can take a sideview shot of yourself.
I bet you will see a difference between that and just looking in the mirror.
And just for reference, I am 6 feet, 1 inch tall, I have a 42 inch chest,
and a 36 inch waist. I do not have a gut, and I tend to stand up striaght
and not slouch like most people do. So the extra inch is not just for
people with pot bellies, or guts.
Flathead
I'll just go crawl back under my rock now.