I'm in southern NH, zone 5, and I have a little forsythia hedge along
one of my back corners, under a bunch of deciduous trees. They're nice
plants, I like them a lot, but their growth habit is kind of exuberant.
I'm now in the position of having to hack a path through so I can get to
the back for pruning. The way to prune forsythias, I'm told, if you
want a natural-looking shape, is to draw an imaginary line and snip
anything which extends beyond that. But then the shoots from that
branch just grow into the forbidden territory next year, and cutting
them would lead to the same problem again, so I'm getting kind of tired
of it.

Not that I have the time and money to rip them all out and replace them,
but, supposing I did, what would be a good replacement? I'm looking for
something shade tolerant that would grow to about 6 feet tall,
preferably with some fullness all along the height of the plant.
Flowers would be nice, too. Nothing that needs lots of pruning year
after year after year.