I think the root issue is that although he's come a long way in the fine motor skills department, writing is still really a lot of work for him.
I decided to capitalize on his love of mail, and try a new method of encouragement. I picked up a notebook for each kid, (because V refuses to be left out of anything,) and I'm going to try to write him a little note several times a week, if not every day, for him to respond to.
I'm not trying to create a ton of extra work for me or him, so we'll be keeping it short. The above entry reads "I hope you are having a good Monday morning. It's a new school week. Can you think of anything you'd like to learn about this week?"
My hope is to maybe help convince him that writing is practical, and useful, and not just "work." We'll see how it goes.
(Nearly four year old V will be the recipient of a little drawing to color or riddles like "I'm an animal with 4 legs, and a long tail. I say meow. Can you draw me?" )