I’ve been ask several times this question. I am not a material engineer and only vaguely know that the slim design of JZ88, if made of aluminum, won’t be strong enough. But here is an interesting article “Metal matters” which helps to explain the difference of steel and aluminum, and other material.

“To compensate for this lack of stiffness, aluminum bikes almost always tend to use larger diameter and thicker walled tubing than steel bikes. By the time you dimension up an aluminum bike to gain the required stiffness and structural integrity, you really start to approach the weight of a well made steel bike.”

“To keep costs down and to produce an acceptably lightweight bike, manufacturers use aluminum in their construction rather than steel.”

I think the bottom line is, to try it yourself and to made your decision based on personal experience rather than just hearing what other said.