I would T each 2.5" line into (2) 1.5" lines so that you have a total of 6 floor or wall returns.
You might be able to use one of the drains as a return but check with the manufacturer to see if the drains are certified as returns and at what flow per drain as a return.
You might be able to use one of the drains as a return but check with the manufacturer to see if the drains are certified as returns and at what flow per drain as a return.