As a former Cubmaster for over 12 years I can tell you that your right about cutting off the number of boys in your den. The Cubmaster should let you limit the number in your den to 8. Has your assistant thought of becoming a den leader for the new boys then one of your parents could take either a rotation basis to help you or one of them could step up to assistant? Recruit one of the new parents to take the role too. Your open to a lot of options either use your parents, your assistant, new parent, or hold a recruitment night to gain some more leaders to take on a new den. Hope this helps you some.