you're right on track. The goal is to increase the amount of unfermentable sugars in the final beer. Maltodextrin is great for this. Flaked oats, Flaked Barley, Carapils, and Crystal malts will add body as well. Be careful with the crystal, so that you don't end up too sweet.
Also make sure you are mashing a little higher and you can use a less attenuative yeast.
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