Actually, I'd argue that the reverse is true. The more people you use, the less security you get due to increasing probability of a random exit scam (even though the loss of founds would be proportionally less). Unless we are talking about a very high amount of USD (equivalent) here (in which case it would definitely be advisable to do multisig and whatnot), I see no reason to make this more tedious than it needs to be. Even the 0.5% proposed fee is less than what people would usually charge (at least >= 1%).