He may have grown since that photo, but compared to his handler (who is standing downhill from him and stooping forward a bit) he doesn't look that tall in the photo you posted, unless she is very tall. 17 hands is 5' 8" at the withers.
I went and looked a the videos they have posted and they are just short clips, and all are just of him loose as a 2 year old, and are in slow motion. They have a couple photos of him under saddle on his page-- do you know if they have a current video of him with a handler, or better yet working under saddle and not in slow motion? (Sorry, slow motion just bugs me, as it can make everything look "fancier"-- not saying he isn't a good moving horse, I would just like to see some of his real natural movement! LOL)
Regardless, he has some nice qualities, and size-wise the difference is probably not dangerous for breeding-- but its best to have your mare vet-checked by an experienced reproductive vet before breeding to make sure everything is OK and ready to go with her, and also to ask an experienced repro vet about the size difference.
Your mare and this stallion are both attractive. You said you wanted to breed for more bone and height with a sport type build--But with the stallion and your mare being different sizes and different types (the stallion is a draft cross sired by a Clydesdale and out of a TB/arab/paint cross with an upright build, higher set neck, and your mare is QH type with a more level stock horse build), it might be tough to predict what traits and movement the foal would inherit from each parent, given the "mix".
It would be great if they had foals by him from more QH-type mares to compare to, but I don't see any on their website-- they are out of Warmblood and TB mares, and they are all still babies since he is a young stallion, so assessing adult height isn't possible yet.
You mentioned wanting a "paint"-- Do you want a registerable foal? The foal would not be eligible to be registered as Paint (registered Paint, QH, TB lineage only) or Pinto (no draft within 4 generations.). The website mentions that they have the stallion registered AWS and are applying for the NASDHA-- do you know if a foal from your mare would be eligible for either of those associations?