How to changes ship size and make it work?

I have been trying my hand at modding SE5 and I need some assistance. I changed some of the ship class size tonnages and the game will load up and play ok, with one small problem..the AI player won't/can't design any ships at all. Even the ship classes I didn't changed? I next tried loading into my mod folder AI empire files but that didn't. Is there a way to modifed the AI empire files so they would use the changed ship classes?

Second question how does one made new technology, weapons and place them into the tech tree without screwing up the game? Is there a how to do it test out there someway for SE5, there was for SE4?

Lighthorse