Thanks for the advice guys.... We ended up doing it the "quick and dirty" way.
No cutting , not much fairing removal on an older (93?) non-abs ST1100.
1) removed front windshield
2) removed lower front top cowel
3) removed secondary front top cowel ( what ever its called, the inner one with the rubber flap)
4) stuffed the Steibel into area on left front area behind dash (facing bike)
5) added a U clamp to the left front bolt that connects the center to left side fairing , wired tied horn in place to U clamp and secondary location of mirror frame ( no, it can't fall out the bottom and has no place to move )
6) grounded to horn to frame ( wire nut with sealant ) near mirror, ran + wire down to original horn location
7) pulled wires off orig horn to relay pins 85 -86
8) + wire from horn to relay pin 87
9) ran wire under tank to battery (20a fuse) to relay pin 30 (pulled thru after threading heavy wire)
10) stuffed and wire tied relay in upper right of fairing
Left in original horn in case of a problem...just switch wires back.
We cheated a bit cause it's an older bike and the horn really can't fall out... if we had time , we would have made a bracket for it in same location... but he was in a rush. Not the best work, but buddy was happy. BTW, the horn is tilted about 15degrees but works fine and the horn output blows down to radiator.