OK, great stuff. Here are a few tips. At Eye-Fi, I'm probably the one with the most experience shooting events and live shows, so hopefully this will help you:
* I've had tremendous luck with either a Linksys WRT-54GL router, or a Linksys WRT-320N router. But the set-ups are different:
With the 54GL, which is a g router:
* swap the small antennas with the "2.4 GHz 9 dBi Rubber Duck Antenna - RP-TNC Plug Connector
" antennas: http://www.l-com.com/item.aspx?id=22068
* These antennas make a huge
difference, and have a really nice doughnut shape coverage, but THEY HAVE TO BE AT THE SAME LEVEL
as your shooters. Do not place them 2 stories above the shooters. That's one of the main problems that you're running into.
* flash DD-WRT onto the 54GL router. It's a free OS (but you can donate), and will make your 54GL router do things that usually cost thousands of dollars in enterprise-level routers. For example, you can use WDS, and bridge several routers into 1 network, you can start QoS, you can boost the power on the radio, etc...
* If you're getting the 54GL, the 2 main reasons for getting it would be to flash it with DD-WRT, and to connect the 2 9dBi antennas
* once you have DD-WRT, boost the radio power from the default setting to, say 120mW. Don't go crazy, but 120mW will give you a nice power boost, to the default setting.
With the 320N router, which is an N router:
* I would still highly recommend flashing it with DD-WRT, but you don't have to. N, by nature, helps with the range, so by simply getting this router, over a cheap g router, you'll see gains in coverage and distance.
* I used the stock power setting in DD-WRT, which was 71mW, and in a very wi-fi noisy tradeshow, got about 250 feet of range, with the Pro X2 in my Nikon D300s.
* The 320N does not have connectors for external antennas, but you would be impressed with how much range you get out of that unit. FYI, we use that unit as our corp router, at Eye-Fi.
Something else that you can do, is to use WDS, and bridge several routers into one network. If you do that, I highly recommend setting up several SSID's, and not using the same SSID for all routers. Then, add all of those SSID's to the Eye-Fi Cards, so that they could "roam" among the routers. BUT, and there is a big BUT -- if you use WDS, you will get increased range, and much reduced bandwidth. Every router that you add to a WDS network, divides the total throughput of the network by 2. So if you have 4 routers, and lets say that you did this on a g network, you would be in the low 10's of max throughput, and if you have several shooters that are streaming images, at the same time, they will be bottleneck'd by your WDS network.
So the best thing to do, for your first experiment, is to just use 1 router, placed strategically. Use a free OS X or Windows Wi-Fi scanner, and start to walk away from the router, with your laptop, and see how your RSSI (signal strength) drops (there are also free scanners for the iPhone and Android devices). Then, start shooting with the Eye-Fi Card, and see how far you can walk away from the router, while images are still coming in.
Keep us posted.