Old thread, buttt...
The Pico really shines with a better tank. The Melo is not bad at all but it will pop and spit at you at ~20-25w and higher. Mine did, anyway.
The mod really shines with a Baby or Big Baby Beast or a Subtank Mini. These are the only other tanks I've used on my two Pico's. I settled on the Baby for its low profile, but it's aptly named.
The Baby or Subtank mini will work, but a BBB is ~25 mm and won't fit. One of the issues with the Pico is that tank size limitation. Seems resolved with a Pico 25 now released though.