FF before Finishing LCI?

[Sue]

My sons (6th and 4th grade next year) have completed Prima Latina and half of LCI. Is it necessary to finish LCI completely before beginning First Form? I am thinking I would like to get on the First Form track as soon as possible, so that all of the Forms (1, 2, 3, & 4) would be done before my oldest is in high school.

Thanks for your help.

Sue