There is also more to confidently riding fast than body and handlebar position. As Keith Code said, and I am paraphrasing: "you have a dollar to spend". How you want to spend that dollar is up to you.
A few things that I put to point when riding above commuting speeds, be it on the FJR, DR-Z, CRF, KTM, etc:
Basic body position: Are you comfortable? I have friends who ride as quickly and have a completely different body position. Personally, I like to lean off on street bikes, and keep as much tire contact with the ground as possible, but will stay more upright if the tarmac is grippy, etc. I feel as though I have more control and more headroom. For me, it's also enjoyable to move around and feel the torque and g-forces.
Inputs: When riding hard do you have solid flowing mechanical inputs to the bike? Can you throttle up or down independently of other actions? Can you apply rear (trail) brake in to a corner without upsetting geometry? Can you pull in the clutch and up or downshift without a major upset of the platform? Can you lean further in to, or out of a corner if need be? All other things being equal, can you push through the pegs with your feet and alter the bike's course? Are your hands loose on the bars? Are your elbows relaxed? When you are comfortable in a fast corner and get on the throttle does the bike turn in, or out? That last item alone will provide a lot of feedback about your ergonomics.
Recoverability. Again, are you comfortable and have margin for error? If you're not, then slow down and/or find a local track with instructional managers that will follow you and provide feedback. You always need to be able to take a degree of evasive/corrective action. If you are comfortable and have margin for error, then continue evaluating and refining all of your inputs to the bike at any given point.
There are some good roads in my local area. A worthy exercise is to run the same stretch a few times in a row, changing body posture and other inputs, and realizing what a great difference it all makes.
Hope this helps....like Tommy Lasorda said, and again I'm paraphrasing: "Baseball is 90% physical, and the other half is mental". While I don't necessarily agree with the numbers in that quote, then I do believe in getting yourself physically comfortable, and then getting really really mental.