Well he appears to be regular sized, although I would have assumed that the disrupter beam used by the kazon would be much larger compared a human being sized mass.
EMH [on monitor]: I would humbly submit that my programme is far more sophisticated than your run of the mill hologram. In fact, projecting the illusion of a large, three-dimensional object has been a trick of magicians for centuries.
PARIS: We'll just do it with mirrors.
EMH [on monitor]: Mister Paris's predictable attempts at humour notwithstanding, that is precisely what I would suggest. Installing holo-emitters along the hull with parabolic mirrors to enlarge the images as they are reflected into space.
KIM: We're going to use up a lot of our power reserves trying to pull it off.
Depending on the focal length, where you're making the hologram "appear" would indicate the size of the holograms., and since they wanted a huge ship, it would be odd that a regular sized doctor would come up out the other side of holographic manifestation that was supposed to be the size of a starship...