I'm sure it's been done, but has anyone called Jax center or TPA approach to see if there is a radar return that matches the departure date/time/direction? It would at least give you a point in the right direction.
Maximize your planning before you launch so maximize ground covered with available resources. Some things to think about:
-Don't get over zealous. 4-6 airplanes max depending on the experience level. If participation is high, have multiple flights covering multiple tracks that never overlap.
-Comm, have a plan. i.e. everyone is up a discrete air-air freq, monitoring. Keep chatter to a minimum. Lead give timely updates to heading and airspeed to maintain formation.
-Line abreast (if that's your plan), 1 mile apart. Two spotters in each airplane designated to a specific side of the airplane. You need to know what an RV looks like at a mile. Quick way to do it is one person goes to the end of a runway, others go 5-6000' down the runway to see what it looks like. Can you see the numbers? Can you see heads in the cockpit? You need a visual reference. 1/2 spread is pretty close and you can close that pretty quick with only 5 degrees of heading closure. From 1000' a half mile lateral is about the wingtip, so you'll get good coverage especially under the nose of the person next to you.
-Assuming you've got 5 air planes that gives you a coverage swath of about 7NM. Someone needs to be lead, particularly in the middle. Plot a very specific course from A to B. Program into GPS and fly that line, everyone lines up off them. Leverage equipment and experience to positions. Example, whoever has an autopilot that can fly the course with heading/altitude hold is the lead. Plot a return from B to A that's offset 7NM. This will maximize coverage to make sure not to cover too much of the same ground again. Back and forth. So in two passes you're covering 14NM either side of the route. When it's time to reverse course, collapse the formation down, lead makes a gentle 10 degree angle of bank turn, the whole formation turns with him. This should give you about a 5 mile turn radius. When you're on the new course, the flight spreads back out again.
-Have a plan for the formation to hold if someone needs to turn back to investigate a potential hit. Spotters, pen and paper to copy down coordinates. A handheld GPS for them will enable the pilot flying to deconflict from others in the flight and not be fidgeting with gadgets. i.e. If someone sees something, everyone in the flight enters a left hand turn, 30 degrees AOB @ 100knts. Binoculars for the passenger is a good way to look at something without needing to turn around.
-Have an altitude deconfliction plan. i.e. Lead at 1500', left and right are at 1200', the out riggers are at 1000'. There is going to be a lot of heads down time, unnoticed closure can result in a scarey situation. Worst case scenario if flight paths cross you have a built in fudge factor. If the airplane(s) next to you are level on the horizon, you have the potential to hit. Make sure they're either above or below.
-Lastly, have a separation plan. Everyone gets a sanctuary altitude. Say, 1000/1500/2000/2500/3000 etc. If for some reason you need to break up the flight, have a way to do it. i.e. the outriggers turn away 90 degrees level. The middle players turn away 45 degrees and climb to their own altitude. Lead keeps going straight and accelerates.
Have a plan, brief the plan, execute the plan. What you're doing is dynamic and complicated, but if everyone knows what to expect you'll successfully mitigate the risk. Don't hesitate to scrub and start again if things go sideways. Good luck. Wish I was there to help.