I'm actually on the other side of this discussion with my buddy Andrew. I built a 56 cm frame out of 6/3/6 Ishiwata 015 (1" top tube) back in the late 70's. The whole bike weighed just over 15 pounds. I expected it to be very flexible like everyone said it would be but it worked perfectly for me even when i was going flat out. Some others racers didn't like it when they tried it but then they were sprinting up hills. Later I made another frame for myself with a 6/3/6 down tube and a 7/4/7 top tube. Loved the ride of it too but the problem with 6/3 is that it isn't robust enough for routine riding. It was not too flexible for me. The Europeans pros used it only for special events. I hit a small pot hole on a training ride (when the wheel I was following didn't point it out) and not only did it put a dent in my front rim but also put I crimp in my down tube. I replaced it with a 7/4/7 and still love the way it rides. At the time I was 5'8" and weighed around 130 lbs. I could hang with the cat 2s and 3s back then as long as I never had to take a pull at the front. So there was always sprints out of the corners and hills to climb at speed.


Tubing diameter/gauge choice has something to do with pedaling smoothness too. I used to put more powerful riders than me on the back of my tandem when we went on those training rides and with some I could barely keep it going straight and others it was a smooth as silk ride.


So by all means use a 1" top tube with at least 7/4/7 unless you are a sprinter type. An alternative might be to use a 6/3/6 top tube. Reynolds used to make them and might still have some in inventory. I wouldn't use a 6/3 down tube just because of durability. Light tubes do take more skill to braze however. I don't allow my framebuilding class students to use light tubing for that reason.


7/4/7 OS tubes don't work nearly as nicely for me at all. If you do the numbers, they are the equivalent of 9/6 in standard tubing which is way overkill for me. I don't like the ride of either bigger diameter tubes or heavier gauges nearly as well. This is a Catholic/Protestant, Democrat/Republican argument that will never have a consensus. What I know is that I personally greatly prefer the ride of light gauged standard diameter tubing (and I've made and personally ridden almost all options). Jan Heine writes a lot about the classic French builders Rene Herse and Alex Singer that used super light tubing and why he loves the ride of those bikes. He gets a lot of grief for his hypothesis of why it works (and I don't agree with that guess) but speculating on reasons doesn't change a rider's preference. Actually there aren't many people that have actually tried riding a frame made out of light standard tubing because production makers don't use it.