I assume you're worried about wrap-around style pop lugs in terms of a friction problem. In general, it's better to err on the side of too loose rather than too snug. This is because even if a wimpy "too loose" elastic doesn't fully open the lug, the drag hitting the model as it is clearing the rod is often enough to nudge them apart.

Besides, applying the principle of maximizing worst case outcomes, too much friction/too tight can mean insufficient velocity when clearing the rod and unstable flight. Too loose means the lug stays with the model the whole flight (really unlikely) or partially, costing a bit of altitude (at most maybe 5-10% depending on whether it partially opens and pieces flap around). Which of those two problems would you REALLY not want to experience?