Good idea to root prune?

I am wanting to move a Sorbus Cashmiriana. I planted it about 7 years ago and now decided it's not in the right place. Obviously I'd be crazy to try and move it now and intend to move it about November. I was wondering in preparation if it would be a good idea to root prune it now, but maybe to be of benefit I should have pruned it in the Spring and now it might be a pointless exercise.Any difference if I left moving it until about March?Any advice would be appreciated. Thanks.

 

It cant hurt, but I do remember reading its best done a year in advance, gives the tree time to grow more fibrous roots.
Never tried it myself so only passing on what I have read.