Your version of that antenna will work, but if you have the coax that
short, it really isn't a g5rv any more.  If you look at the origianl
articles and design, you'll see the length of the coax as well as length
of the ladder line is all part of the design.  I bought my first one
commercially back in 91 when I was in college and it had around 30 feet of
ladder line which went directly into the coax which happened to be rg8 x.
It had a current ballon on the antenna end of the coax which as Kevan
said, primarily just keeps rf off of the shield of the coax.  As I recall,
they recommended at least 50 feet of coax cable.
73s
Butch Bussen
wa0vjr