Here's a question. When mounting a cannon on the prow, how do you plan on showing the difference between the Lance and your version of the Nova Cannon? Shorter barrel and wider bore?
The Nova Cannon is a totally different ballgame, apparently it can only be mounted on cruisers or battleships since its engines help out against the intense recoil. Thing is that the Nova Cannon is basically a giant railgun. I'll be designing something completely different for that one.

Its' hard to judge what would look good. When I first saw the cannon mounted in the center of the prow structure I thought of a unicorn. That's partially why it looks strange to me. Maybe if the mount was lower, not quite on the chin but close, it would give the impression of a rhino.
I might play with that. Not fully sure yet since such a modular kit for 'just a frigate' would make the kit a bit risky (more that it might make the kit too expensive). But it's something I still need to ponder about and toy with.

If you believe that mounting the lance at the top of the prow doesn't look good I trust you.
The lance itself would look good, that's not the problem. As seen with the Destroyer, it works. But compared next to the other lances it becomes a bit odd.