Not a big believer in all this "must fly a pattern hype", we have put 4 to 6 planes up at once for many many years with out any rules as to pattern except everyone takes off and lands into the wind. No midairs. We also fly combat wings in tight groups with the intent to hit each other, guess what it is very very hard to do. Less experienced pilots seem more prone to midairs as they don't anticipate taking evasive action when it may become necessary. No opinion on who owes what to whom, but our club would say you put it in the air it is your expense, each guy replaces his own. Now if he shot you down becasue he didn't get a frequecy pin that is a different story.