cut out 1/3 this year then another the next and so on. take the 1/3 out around the shrub rather from just one section.

Interesting branch structure and bark, Slimdil. Would it be possible to skirt it up and brush it out, to make a small tree out of it, Sbg?

Before reading ABS's anwser I thought of cutting one trunk this year at about three or four feet,choosing one of the slimmer ones. See if new growth appears and if it does cut a trunk a year until its the height you want. This will take longer than the above suggestion but leaves you a reasonable shape to look at while its happening.