Apricots can be grown in a narrow upright growing system. See if you can find information on growing apricot on the tatura system in Australia. They space trees about 6ft by 12-15ft, I think. Each tree has 4 upright shoots, two going to each side of the trellis. So you could do similar in a slender spindle.

Thanks, FN. I found some interesting references. Especially from New Zealand where they have been successful with apricots on the tantura system.

Apparently, apricots produce most of their fruit on spurs on two and three year old wood, which must be renewed after the third year. The challenge will be to maintain fruiting wood in such a narrow silhouette and keep the trees productive over the long term.

gary