In my opinion 5gallons is plenty, roots coming out of the bottom is a positive sign.
In my experience because the roots are looking for more medium which they can't find does not mean that the plant will stop growing, simply that they are robust and living life to the full, considering that they are in 5gal pots.
I believe the whole issue on pot size to plant size is blown a bit out of proportion within reason.
I think you should crack on with the 5gal pots and if the plants do stop growing ( which I doubt ) you can consider repotting, but take into consideration that the plants will grow a fair bit amount through flowering.
Have saw large plants in a lot smaller pots.
Throwing an opinion out there,
The pot size within reason, does not considerably hinder plant size within reason but may create a stressful environment for the roots and plant resulting in a less efficient rebust plant. Therefore it does hinder plant growth but not necessarily size again within reason. Lol, for swim 11ltr is enough for medium plants, 5gal is a fair amount, point is that I wouldn't worry crack on until you notice clear signs that growth is hindered but if you feel like repotting assuming the process goes smoothly would only do good. Good luck