I will throw in a couple of ideas here, hopefully to get you ahead of the curve…
*Contact the Council Registrar and ask for contact information for ALL Webelos in your district. Yes, I said all…I know that there is no issues in my council with calling and saying "My name is Shawn Cleary, I am the Scoutmaster for Troop 1363. I was wondering if you could pull a list of all of the eligble 4th and 5th grade boys, so I can make contacts with the for recruiting." I don't know how things in your district run, but the DD should have been able to access that list and given you the most updated information…once again, the Council Registrar can get you that, too.
*Explore the possibility of starting a Cub Pack in your area…if there is interest, you may have something there. I am not saying to start one on your own, but with the DD's help, gauge the interest.
*I notice that you mention your UC. Contact the District Commissioner to find out if one can be assigned, and if not, well, then, at least you know. If you do get one assigned, make sure that they are helping you, and not hindering you or telling you that your program needs to do this or that…you already know what your program needs, and you don't need someone to show you that. The UC should be there to guide, mentor and advise you…and maybe give out some contact information on other units in the area.
*Start earlier….when I say that, I mean, start that contact with the boys who are BEARS right now…depending on the "Scouting Year", they may be Webelos as soon as June. [Our pack has a scouting year of June 1st to May 31st. A Cub Scout is a Tiger on May 31st and a Wolf on the first, we do this for Resident Camp purposes]. My middle son is a Bear, and I have started the contact and "Selling Boys Scouts" already to his den…the Webelos to Scout [W2S] Transition starts the day that they signup as a Tiger. That is one thing that I noticed in your post…"you were too late" because of crossovers.
*Each year, the council will have counts of boys who were Webelos, but don't show up on a Boy Scout roster. What happened to these boys? They didn't cross, and that may be a chance for you to make some contacts. If your council has a "why didn't you join Boy Scouts" call-back night, see if you can get on that team to make those calls
*Advertise, Advertise, Advertise….flyers, TV, radio…get your name and troop out there. Help an old lady cross the street? Call the newspaper…ok, maybe not that extreme, but get out there in the community. Adopt a Park, pick up trash…do something to be visible. And do it with your uniforms on and the Troop Flag flying nearby. Get business cards made and get a website. Google Apps site is $10 per year, and includes 50 email addresses…but then use the email address. Contact the fraternal orders, the VFW, the Rotary clubs…they always have opportunities to help in the community, and may make donations to help subsidize your troop activities.
I don't know all of the dynamics of your troop, but Den Chiefs don't sound like they work for you. Only in the sense with a smaller troop, you may already be stretched a bit thin. But that is always an option, if you have interest from your scouts.
It really is about service…once you believe it, the scouts believe it and then things fall into place.
Are you going to be able to turn it around in a couple of months? Chances aren't good…but if you stay the course, your program will flourish.
Hope this helps