So what's the rule for a regional group-buy?

[WolfWings]

Long story in bullet-points:

• I'm in the Kansas City, Missouri area.
• I want V-Kool 70 tint on my Yaris.
• It's expensive, $1,475/roll for a 100-foot roll which is the only size the local distributor carries it in.
• That's enough to do 5 cars with all five windows for sure, with a bit extra.
• I found a tint shop that will order it, and install as a group-buy situation for $125/Yaris for the liftback.
• Price out-the-door is $420/Yaris installed if we get 5 Yarii total. This does not include removing existing tint if you have any installed.
• I have my 2007 liftback and a 2009 liftback interested, so only 3 takers needed.
• Yes, this stuff is legal on all five windows in Missouri. 70% visible light transmittance including the stock glass.

How can/should I go about setting this up as a group-buy? I'd rather not bury it in the 'midwest' regional forum since that doesn't get much in the way of readership.