A few questions about G limits / corner speed

[Letum]

Are the G limits the same for all planes armed without bombs and fully fuelled
eg does the p51. 109,190 and spit all have the same G limit

No.

Trying to find corner speed experimentally would take a very long time.

It would be nice to know when you are just about to damage the plane not after, hence the need for a better G indication.

Well, you have about as much indication as they did in the 40's. you can't
*feel* G forces, but that shouldn't stop you knowing roughly how much G
you are pulling in a given maneuver at a given speed.

And finally, as any fool know, you can exceed max G without black out ask any P51 driver in the game.

Instantaneous G breaks planes, sustained G causes black out

Yes. it's impossible to warn you in anyway about anything instantaneous.