I am rebuilding an R20. I have an RST suspension fork for it that came without a steerer tube. It looks like I will need a 21" (533mm) tube for this. I am sizing it basically to match the length of the steering column on my DT IX. Is ChroMoly really needed for this? I ask because a local supplier wants to charge me almost $10 per foot for it. How about mild steel? What else have you used for this purpose? Any suggestions?