Low points in the narrative

There are two areas of the books I struggle with. After the initial rush to get all the first ideas down I sit back and think, what next? I know, broadly how the story will end, and am thinking about the ending through the whole process. I stall for a while, at about page 40 or 50, and struggle to write a minimum of a thousand words a day, which I know will be the most heavily edited parts in round 2. I gain confidence in the story strands and the writing comes steadily, but then, at about page 200, I falter again. How do I get from all the middle stuff to the last chapters, which I've been writing in my head for weeks? This, I am sure, is where a sensible plan would have come in useful. That's where I am, in the planning doldrums. People are starting to sit about and drink tea again. It's like they are waiting to jump into the last chapters, too. I usually write those very fast - it only took three days to write the last 11k words of the Secrets of Life and Death. Still, the end is in sight. Strands that reach out into the third book are becoming more obvious. I'm hoping to plot the series on some sort of table, to try and keep tabs on where it's all going. Then I can put book 2 away for a few weeks and work on something else - like book 3, or something completely new.

Meanwhile, the writing group's homework is poetry. It's a simple task, but all things with poetry look simple until you try to do them. Argh! We're supposed to look at examples of imagist poetry and have a go at writing them. This is Ezra Pound's example. He described it as being inspired by oriental forms like the hokku.

In a Station of the MetroThe apparition of these faces in the crowd;
Petals on a wet, black bough.

The idea is to link a very concrete experience or place to a metaphor. I'm off to scribble and struggle because any fool can write forty lines with some poetic bits in (OK, it takes a lot of editing to pare that down to a real poem), but two lines (and the title) has to be concentrated and perfect. Hm.