Hempy Bucket Question

My set up.
Dr150
1000w Digital Ballast
Magnum XXL
6" ruck
Anyways, so im quite new to growing, done bout 6 soil grows so far but I've learned so much now compared to my first grow. So im switching to hempys, got 20 hso blue dream fems in the post. I really can't decide if i should go with x16 7.5 litre hempys, or x9 14 litre hempys or x9 20 litre hempys? So i guess my question is if you had my setup which would you choose out of the 3 options, and how long would you veg from first set of true leaves from seed?
Thanks in advance for any replies

I've read lots on hempy, and 2-2.5 gallons are what most use for plants. Original guy even grew around or over a lb. Out of a 2 liter bottle. His name was dali hempy I belive.

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If you are looking to flip them into flower as soon as possible then go with a small container. I personally don't see the need to use anything larger than 3.5gal (13 liter) unless you are going to do some serious veg time.