I think so. Maybe I'm even a bit below, but I didn't see any fire or hear any dmg. I think I'm a bit above.
This is the map.
Yellow - blaze spawner
Grey - cobble barricades (the area where I and Lotz fought blazes)
Green - the hole you dug into the tower
Black arrow - where we came from'
Orange (except within ramparts) - lava ocean
I'm the red cross, if you could cobble the whole area at the purple at lava level it'd be great, but be safe.