High, my name is Paul and I was where you are now 3 years ago and in fact until my son's Den crossed-over (I doubled at pack and troop levels) our troop was between 4 & 13 scouts in size. We crossed over 14 with us so we now have 27 boys.
I agree with Dan, have a SPL and one or two patrols but let the boys decide.
Our troop started with 4 the first year with the SPL/PL leading the group. Once we got new scouts crossing over we let them form new boy patrols so they would all be same age. As the troop grew we let the PLC combine and create patrols based on age & rank. The FCE boys started out together in one or two patrols with the older boys forming one or two patrols depending on rank and rank needs.
I suggest letting the PLC decide how many patrols to form but give them opptions like; new boy, mixed rank, Venture patrol, ect... When you go camping the patrols can combine if needed or they can work in their own small patrols. This will give a since of pride and belonging.
Recruiting Webelos,
I suggest getting involved with a pack as either leaders, Den Chiefs, or Webelos support. The more contact you have with a group the more likely you are to get some of them at cross over. Also set up and agressive outing program, as a small group we are able to do Rifle/Shotgun, canoeing, climbing, backpacking, ect...This really brings groups out to see us. We now have 27-30 active boys in three years and continue to grow.
Yours in scouting,
Paul
Good luck and Good scouting.