tough question... with only 48 inches.. I would think you could do all 15 and just keep them short as shit.. let them (clones) grow to about 10 inches.. and then cut them down to 4 inches... yeah I said it!!!! and let them grow a 2-3 inches (4-7 days)

and then flower.... with those cool tubes, you may even consider more than 15 plants.. but you better have some serious air flow... you don't want mold!!!!!!

you will get some cool thick KAK buds... the plants will be amazing... dwarfs with big thick KAK's

if you are going to grow normal, 16-20 inch plants- before flowering... then 6 plants is what I would do..

i LOVE YOU!!!!!!!!!!!!!!!!!!!!!!