Nothing wrong with having a go faster kind of bike in the mix. As long as there's no discomfort while riding, a range of sizes can work for some people. I'm 5'10" and ride bikes from 55 to 58. I have had nice rides on 25" Schwinn Le Tours, but prefer smaller. My UO-8 was on the larger side for me, but it was super comfortable. If you can get the contact points in a good place, and end the rides with a smile on your face, then ride on. You have to remember, bikes may be machines, but people aren't. Not everything can be quantified. Some people have a longer leg than the other. Some are more flexible. Some find that what felt good for years suddenly doesn't. Some get professionally fit and still don't feel comfortable. You know your body better than anyone, so as far as the Miyata, well, N+1.