I see you got lot of players for training, in my opinion 3 is enough to train them on 1 position (for example OD on PG), every player play one game in week 48 minutes. It's the most effective training when you go on 1 position.
If your players have lvl 1,2 stamina lets say it could help them a bit, otherwise its not worth to waste your training on stamina on the beginning.
Cheers mate!
This is where we hold them!