dejoha, I recently did a t-shirt and another wood stove buy/sale.
Not technically a group buy per se, but similar.

My recommendations:
Paypal, its official, safe and has all the info.

Folks change their minds..for reasons unknown and back out, if they buy thru paypal, its a done deal. Get payment up front.

Include paypal fees and know what your actual shipping cost will be..if someone orders 12 p.l.'s, a $4.95 usps flat rate wont cut it.

Be sure to figure your packaging cost into the fray. Boxes, tape, labels, printer ink add up. Plus your time. Don't forget taxes, Uncle Sam wants his cut too.

my 2 pesos