I have a 13.55 colony and I had the same problem with 1.4 and 1.3 setup. I do get alot of rats from it but seems to be alot of loss too. So I have started to use a birthing rack so far it seems to be working way better but it maybe to early to tell. I just started to use the birthing rack 2 weeks ago and all the pinky's seem to be making it so far. I made a 6 tub test rack with 3 tubs have one female each and 3 tubs have 2 females each. If the 2 females per tub work I will probably use the mixing tubs from lowes for the rack. If the lone females do better I will build a rack with the smaller cat litter tubs.