I suppose the June 2001 Highpoint Rendel Report is not freely available online as it was commissioned and paid for by Shelco.
However it seems Boeing had major concerns even about that concept as they said ''Because of the nature of the approaches to an aerodrome on Prosperous Bay Plain and the possibility of crosswinds in excess of 13kts, the aircraft may be performance-limited for flights in-bound to St Helena. To allow a robust assessment, flight trialling of the Prosperous Bay Plain site is recommended, to occur before the design for the chosen runway is finalised.''
Boeing concluded: '' This recommendation applies regardless of which aerodrome concept is selected.''