I have been asked to prune this Japanese acer. It's magnificent but is spreading over a large area of the front garden and in summer seems all consuming to the client. I did lightly prune it in summer, but they are asking for a much more drastic prune. Can experts in tree pruning, and especially this type of acer which I know don't normally get heavily pruned let me know how best to tackle it? When it's in full leaf it's a mat of green but I don't know how easy it would be to remove areas of growth to create the space between branches that I know is a desirable shape in a Japanese acer. I just envisage it'll be really tricky and quite hard to achieve a good result.
My current instinct is to prune to joints to reduce the width by some margin and try and take off a little of the height but more than that is daunting. I know about the rule of thirds so wouldn't be thinking of taking so much off it looks pollarded like a London plane. I know this approach could ruin the shape. The framework is old and complex and whilst the plant seems healthy overall, every year there's some inevitable die back on some branches. I don't want to make this worse which is why I know about pruning to joints.
Any other advice much appreciated, and if possible photographic examples of your own work if it'll help me! I have to start/do this job on Monday 28th Nov