firm starter

I took my cold starters, 20g each and added 40g water and 100g low gluten flour and mixed.  Kneaded the crumbs into balls and put them into containers and parked then into the 5° (41°F) fridge.  My plan is to do a cool rise first to encourage the Lactobacillus and do a warm rise later for the yeast.  Also wish to slow down activity for storage.  That was Thursday, today is Saturday, about 40 hours have passed and I might have to move the SD balls to larger containers!  They leveled out just a little but have almost doubled!  This could be interesting!  Am I on to something?