Owlie... if you are in the drops and looking to see if you can see the front hub the stem/handlebar might block your view. Again, this is a very basic way to check length, but definietly NOT an absolute. A bike fit is always better because it entails so much more than sight.... flexibility, top tube/stem/ lengths and what is comfortable. There are many factors related to fit. If you insist on doing this yourself, then record everything and ride for a while, and make very small adjustments. If you truly have an idea of what you are looking for, then put your bike on a trainer and watch yourself pedal in a mirror.

But I still suggest a bike fit