Posted: 12/01/2014 at 13:39
Climbing roses should have their main stems trained as close to the horizontal as possible. This encourages the formation of side shoots which bear the blooms, so restricting it to 6ft is do-able.
However, one of the flaws/attributes of Ena Harkness is the fact that the blooms have a 'weak neck' and so hang down and are best seen from below - it works very well on a pergola as you can look up from beneath - only you can tell whether restricting it to 6ft will let you see it's blooms at their best.
I know you've done a lot of research, but if you decide that you will not see the roses at their best if it has to be confined to below 6ft , you might like to consider Etoile de Hollande instead - it has many similarities to Ena Harkness but the blooms don't droop so can be enjoyed at eye level and below. http://www.davidaustinroses.com/english/showrose.asp?showr=334