Andy_K 

Yes, but my point was that Reynolds (usually) used thicker tubes for the down tube than they did for the top tube while Columbus didn't. I don't know if this chart is accurate, and it certainly isn't complete, but it illustrates what I'm talking about.



Apart from the Super Tourist tubes, the Reynolds tube sets generally used relatively thicker tubes for the down tube than they did for the top tube and seat tube. The Columbus tubes, while thicker than the Reynolds tubes across the board, used consistent thickness for the down tube. (I believe SLX has the same thickness as SL, the difference being the added coils.) Without any first hand knowledge, I can see from looking at this chart why a builder who was using Columbus tubing might choose to mix Columbus tube sets to get characteristics that mimic that of the Reynolds tube sets.

So, if you're saying that Bianchi should have used Reynolds tubing to make a better bike, I can't argue with that except to say an Italian frame maker would have been less likely to do such a thing. But if you start from the assumption that they're going to use something from Columbus, then SLX/SPX isn't such a bad choice. As an aside, I think SLX was generally viewed as being better than SL, even though it's slightly heavier because of the coils, so it seems the Italians were generally willing to accept a minor weight penalty for stiffness, at least. I think SLX is roughly 150 grams heavier than an average 531 frame, but that's a relatively insignificant difference on the road. I'm not a frame builder, so I can only offer second hand opinions about the tradeoffs in choosing between the various tubing. My personal opinion is that 531 (in any variety), SL, SLX, and so on are all good starting points and from there I judge a frame based on how it rides with me on top of it, which is likely different from how it would ride with you on top of it.