Totally impractical suggestion: With a hammerhead you could make a 180 degree turn no matter how narrow the valley is...
A hammerhead (or stall turn as it's known here) still requires approximately two wingspans. Whereas a half cuban eight or an immelman (or something inbetween those two) requires only one. Theoretically.
Yeah, I know. Impractical anyway. Better use your superior judgement to avoid needing to use your superior skill and all that.