I don't know if it's any help, but I use this in my Custom CSS box to control how much of each feed entry shows in my reading list.

/* max-height for syndicated journals on reading page */
.page-read .journal-type-Y .entry-content {
max-height: 30em;
overflow: auto;
}

Then you can either click through to it or it has its own little scroll bar, so you can read the whole entry without it taking up lots of space on your reading list.

I use 30em, but just change the value to get a size that works for you.