Bit of info for you RIPPERTON, Aprilia confirmed to me the reason they used Titanium for the column over Aluminium is because of strength. The bearings they use are very small compared to the OEM bearing (I thought oem was 26x47x15, this bearing is infact the race bearing) and the OEM is alot larger. Because of the stress on the column they used Ti over Steel.

With larger OEM bearings, alloy would have been fine.

We will make a column to suit OEM bearings and will use 7075-T6 as suggested.