You're right about the Callisto being a high altitude rocket. I've had one since 2003 and only flew it on F & G for a lot of years. Scratch built my L1 later but that's a different story. Since then I haven't put anything bigger then a H165R in it. It's only 29mm. Wish I had gotten the 38mm right away.
You need to keep an I366R-L and some binoculars on hand for that perfect day when there is no wind. That will get you well over a mile.
The rules say you have to pay $5 to have your card re-issued with the Cert # changed, and I was planning to do that, but yesterday in the mail I got a new card with Level 1 printed on it - without asking for or paying for it!
Someone had written "Congrats on level 1" on the inside of the envelope.