I find the length of the spinpole only an issue if you really try and sail the same angles downwind as the 2 ups and even than in most cases it's because your main is not properly trimmed but you can't adjust as you already have the helm and spin.
As you are alone on the boat steering the same angles as the 2 up boats is definately not necessary. You can sail at least 5° deeper without loosing too much in speed (deeper angle definately makes up).
With a well balanced rig the length of the pole is no issue.