Not really an ST1100 front reply, which I have no experience of, but a lot of XRV 750 Africa Twin people put KTM USD front shocks on their bikes. Maybe there is something to learn from there?
As a matter of fact I have a KTM fork and wheel sitting in the garage waiting. I'm using the original KTM brake caliper and disk, which makes it easy. And head bearings are available. What puts me down a bit is that I have to ditch the original speedo and trip meter.