How hard do you work to make your fundraising copy "flow"? In my experience, too hard. Flow is considered a hallmark of good writing in many quarters. It's that sense of smooth progression from one topic to the next, with easy, almost unnoticeable transitions.
As the Happy Donors blog notes, it's not really what you want in fundraising copy: The #1 Secret to Writing Fundraising Letters that Maximize Results. Flow is usually exactly what you don't want in fundraising. Here's why:
Readers will pick up the four page letter, look at their name in the salutation, flip over to the P.S., then shuffle the letter around in their hands, maybe start reading here, maybe start reading someplace else, jump around a bit, and then, after this ragged scanning, MAYBE start reading at the beginning.
If that's true (and it is), flowing copy is a pretty bad idea. It won't communicate as clearly as choppy, jumpy, repetitive copy.
Write your fundraising copy so readers can start anywhere and quickly get the point and an ask. Don't have paragraphs that make no sense without the paragraphs before them -- you can't be sure your reader will see them in the order you put them.
Don't waste your time on flow. It'll make your copy less effective.