Hey green, how close you can get your light depends on a couple of things, how efficient your cooltube is and how mature your plants are. It's already been mentioned that you should have your light further away when they're seedlings, i'd start at about 2 feet and try to get down to about 10 inches when they're around 4 weeks old. Just keep a close eye on them and raise the light a few inches if the leaves start to curl.
As for cloning your success will depend on the strain and how old your plants are gonna be when you force them to flower. Some strains are difficult to clone and need to be more mature before you can clone. Giving it a try won't hurt and if it don't work, next time try cloning a week later. Just plan when you wanna flower and a couple of days before take your clones. I like to give my plants a little time to recover from the stress before flowering but i know some people clone a few days after switching the lights. It's just about finding what works best for you.

Good luck with the grow!!!!