It may not be entirely a practice effect (or lack of practice effect) that you are looking at. If fine motor is difficult for him, he may be putting an awful lot of mental or physical effort into the little bit of product that you see, and he just might not be able to sustain that level of effort. Is he still getting OT? Did the OT give you a home program to work on building up strength and stamina in the muscles that are needed for trunk, arm, and hand stability? (A lot of these things are fun "game" type activities, like "wheelbarrow walking", squeezing and building with modeling clay, and drawing on paper hung on the wall, or in shaving cream spread on the shower walls and doors.) They might help a great deal with minimizing the effort he needs to put out and the fatigue he experiences even though it wouldn't seem at first blush that they would have any application to writing. If he can "practice" in ways that he doesn't already identify with writing and therefore with failure and frustration, he may make bigger gains faster, and see more results from the practice that he realizes he is doing, and this might make him more likely to practice actual writing more.
