hmarks,

All Miyatas are nice, very well made bikes. They are perhaps Japan's finest massed produced bike. A Team or a Pro, like this smokin' hot deal that finishes on eBay in one hour:

http://www.ebay.com/itm/miyata-pro-r...item3f17ba65ef

will save about 2 - 2.5 lb over yours, which would be helpful for climbing or criteriums. Looks like it comes with 36 spoke wheels, which are a safer bet for bigger/heavier riders.

My 88 model 312 is a 63cm C-T frame, top tube is a fairly short 58cm. 2 sizes too big for me, I use a 90mm stem and only have about 2 inches of seatpost sticking out. Use it for a sport tourer/ randonneur, and with nearly equal height saddle & handlebars, it rides like a Cadillac.

My 92 model Team is a 58cm C-T frame, top tube is 56.8cm. Fits like a competitive glove. 100mm stem there, a little over 4 inches of seatpost out. Like any true race bike, the ride is a little nervous/ darty at slow speeds, but tracking is stabile and precise at high speeds.

I don't think it has been said yet - the fastest bikes are usually somewhat undersized for the rider and use a slightly longer seatpost. This allows the stem to position the handlebars in a "slammed" position and creates a significant height difference between the top of the saddle and the top of the handlebars - like 12+ cm. This difference places the rider in an even deeper than normal tuck with hands on the drops, so improves aerodynamics by reducing the rider's cross section to the wind and by reducing coefficient of drag. The tradeoff, especially to those of us who are older, is it requires more flexibility to get into that position, and can result in neck and lower back pain, and unnecessarily arduous long rides.