A Red Dragon that large and well established is a valuable tree, so I'd approach pruning cautiously. Once the tree is fully dormant, you can go in (yes, up inside the tree - often means getting on your back!) and carefully thin out to layer the branches and enhance and emphasize the trunk form. One of the best features of a mature weeping dissectum is its winter appearance, often with a sculpted, contorted trunk and intricate branch patterns. And you can (and should) always remove any dead wood. Other than that, pruning should be minimal and I'd avoid trying to limit size.

The older the tree the gets, the wider it will become - an 8-10' spread is not uncommon. Although most would not take the trouble to do so, if it is now encroaching on the walkway, I would indeed consider relocating the walk rather than attempting to relocate, perhaps with far less success, the tree itself.

Is that a typo (6ft X 25ft)? Perhaps you intended 6 ft X 5 ft. Either way I would wait until the tree is fully dormant and prune it in February or sometime around that to limit the bleeding if any medium to large limbs need pruning. Chances are there are some crossing limbs in the interior that could use a little pruning. Pruning JMs are one of my favorite things to do and I have a hard time waiting until winter, but I think it is worth the wait.

I had to read that twice as well, Matt :-)) My interpretation was 25' around, meaning a canopy circumference of 25' which would translate roughly to a spread of between 7-8 feet, a much more reasonable figure. And the ideal winter pruning time is going to be somewhat flexible, depending on location. February here is almost too late, as the sap is typically already on the move and one can experience bleeding. More of a concern to the pruner than it is to the tree, however.