I was playing a game the other day and got into wars with all of the other majors so, as you can imagine, I was somewhat outnumbered. I noticed that several of my minor allies had Overlords with far more hitpoints then mine.
I gave a system near the Torians to the Scotlingas (who had very hitpoints on their ships) together with several Overlords. The Scotlingas killed off the Torian ships as fast as the Torians could produce them. One problem solved.
Elsewhere the Carinoids were fighting the Drengin and Yor with regular donations of ships from me. I gave another system, close to the Carinoids, to my Alexian allies who had weak Overlords but a very large navy. This helped suppress both the Drengin and the Yor. I donated another system each to my Arvenitian and Debian allies who also had higher hitpoint ratings than me.
By donating these systems in the warzone I ensured that my allies would be sending ships into the warzone. Donating my relatively weak ships to these allies boosted the hitpoints of the ships.
It was enough to tip the balance of power. My allies used these ships (and the ones they produced themselves) to clear out enemy fleets, my transports can go in defended by my weak Overlords. I only needed a small fleet myself because so few enemy ships could get through the sectors controlled by those allies ( and in any case my other weaker allies closer to home had a few ships about the place that shot down the few enemies that did get past the frontline allies).
I reckon I would have lost if I had not done this. Anyway, this is just another tip for the toolbox.