Most collectors (myself included) prefer flat shipping. Most collectors are also willing to pay a bit extra for flat shipping.
Even the older soft felt pennants can incur damage, if folded or bent too severely. Although the felt can withstand being folded or bent, the painted graphics tend to crack and/or pucker when bent too far.
Lots of ebay sellers like to ship them "rolled" (often around a paper towell cardboard core). Usually this is ok, but I have had a few in which the paint cracked or even flaked off. Just something to look out for...
Hope this is helpful
