Crossback to windmill (aka wheeldown) is one of my favourite sling transitions!
Prerequisites: You will need some familiarity with basic windmill/wheeldown technique (bent or straight legs) on vertical apparatus so that you have an understanding of the necessary tail manipulation/tension to keep you in the loop. You won’t be weight-bearing on the back arm in the faux back flag end position, but you should still ensure your warm-up includes some shoulder internal as well as external rotation pathways.