Whats up?

Just a couple things... First your question about MG. Ive used MG potting soil many many times with great results. Ive also used Scotts potting soil mixed with MG perlite with even better results.

The size of your box and the size and amount of your CFLs will raise the temp alot inside from my experience. I would be careful with using just pc fans to cool all that CFL in such a small box.

Also ive read that the optimal light cycle for lowryders and other autoflowering strains is 20/4.

Hope this helps and good luck!!

*edit* Didnt notice you wanted to run the exhaust into a carbon filter... I dont know of any pc fan that could pull that off... but I might be wrong. Got any links for the fans you are considering?