Country Loaf Torpedo ?!

Hello all bakers

I have been baking a country loaf using a 20% pre-ferment. My previous attempt was a torpedo shaped rock that was inedible. I tried again and halved the instant yeast from 4g to 2g. I also I halved the dough and shaped 2 smaller loaves. This time they were both edible ! The crust was crisp and the crumb was soft and chewy. Success ! However i still am curious about why they rose to look like a torpedo, very round. The dough was also very limp like a ciabatta, even after i folded it after the bench rest to get more surface tension. but when i got into the oven it just expanded. And another thing i noticed was that the crumb had irregular holes but mostly at the top and not the bottom. Any ideas on that one ?

thanks

Warren