[Campeador]

There are limits that should not be crossed, like speed and size.
It sounds logic that if you double the speed of the game, all aspects of the game play from screen action, to AI execution it would be double the normal speed, but it is not. Too fast and the graphics cannot catch up, and the AI cannot catch up either.
So the best way to go is simply to try, see the results and adjust accordingly. I do not try to pass 1.6 (Zentradi fighter) on fighters because it may be too fast for player reaction, AI reaction, turn rate, sounds and more that you will see if you try. But by all means by trying is how we learn.
As well as the speed there are limits about size. For example I did try to make few ships really big like a Zentradi flagship (4km in length), or a Borg cube (3km cube), and many others but the results were not satisfactory. For example if the enemy ship is too big you may fly inside the ship (all in 3d by the way…) really cool - but not the initial intention. A ship too big also affects collision, weapon range and many other factors which not only affects the ship in question but also the other normal size ships when on the same screen.
For example if a fighter weapon range is 60, it may never fire at the big ship due to collision or range of the ‘hearth’ coordinates of the big ship, ('Base Model Radius'?), may be greater than the fighter range. By the way to this date I do not know how the 'Base Model Radius' setting affects the ships on the game even thought I have use a great array of different numbers.
I do not know much about SEV to bring any helpful input on ships conversion. On star Fury you can internally scale your ship by editing the 'SpaceObjects_XFiles.txt'
On my whole series I used the Terran battleship as the standard scale for the Yamato. Then I used the Yamato as the standard to scale all the ships I made on the game.
I am not that bright on the ways of graphics. I do not have a smart way to set up firing points, so I use the old fashion way of placing a firing point on a spot, try the game, see where it shows up and then re-adjust until it lands on the tip of my cannon. Time consuming but works for me.
Please note that my observations are only what I have tried. Not like somthing is impossible, simply that maybe I have not found the right way of doing something.