I concur with the others, though it's hard for me to say this - it's possible to get too big of a cannon.
When I ordered my cannon from Hern, I was a little disappointed when I got it, and realized I had ordered a different one than I thought I was ordering (my fault, not theirs). The one I ended up with is a little smaller than the one I intended, and they offered to exchange if I wanted to, though I chose to stick with the one I got. At ~24" and ~75lbs, it's easy enough for me to put in the "trunk" of my Camaro, and the carriage just fits on top of it. The one I intended to order would have been about 30" and 105lbs, making transporting it in my car much more difficult.
With a 1.5" bore, it's still a blast to shoot (pun intended), but it's a manageable gun that is big enough to sit on the floor of my foyer and small enough to transport.