Surely your aircraft will be happy to turn for as long as you want at a 90-degree bank angle; as far as it knows, you're just pulling up. Therefore if you have a +6g airframe, you can pull as hard as that, and so on.
Problem is, you'll be descending at the same time (no lift in the vertical plane, see?). So, start the turn at 50 feet and you'll die quickly; start it at height and the effect of the sideways movement will be yaw in the direction of the ground. If you're pulling truly as hard as possible, you'll be just above the accelerated stall, so it will be an incipient spin.
I could bullsh1t for England, me.