I actually don't give a crap how big Enterprise is. As long as it sticks to the basic design. So what if it's 700m / 800m / 350m long ? It doesn't matter - it doesn't exist.
When go to see Star trek - I expect the Enterprise to be in it. I care 0% about how big it is. It's science fiction. It's not meant to be 100% plausible or scientifically sound.