Does anybody know a way I can use my ML CF cards that I use with my 5D mkII on my 7D without erasing ML when formatting the card in the 7D?
I think they will work, but we do not recommend doing this - there were a few reports of users who had trouble with this practice of swapping cards (not related to ML).
http://www.magiclantern.fm/bestpractices
Will the 7D know not to delete the ML files though when performing a card format?
No
Thanks thats all I needed.