This ship has brutal frontal firepower with its 2 medium guns and 1 small gun on the front.
That worries me, even before you get to the high speed bit.
I've thought about similar 2x medium gun ship designs, but the having effectively a heavy-pyra able to deliver a double heavy carronade or double hwacha salvo in the direction of travel just sounds too OP. Add in a light weapon (mortar or flak) to the same salvo and I think it would be almost impossible to balance.
PS
the image is a 50x50 pixel thumbnail, it needs to be about 500x500 pixels to be readable.