Mine is 20" and it's fine with pod I have on 18ft malibu 185 which is a larger boat then yours. My main has a 25" based on my hull design, and your DE you would be fine with that. Doesn't drag or lift out of water with swell/waves etc.
A 25" I could see on larger boats, but your draft isn't that much on a 17ft DE. It isn't needed.
The pod fabrication place should know all this. I went with their advice based on the design of pod.