Have been looking at a lot of telescoping mechanical mods, it looks like frequently the vent holes will only be exposed in 18500 or 18650 modes, am I missing something? Why is there often no venting in 18350? Puzzled. Example: https://fbcdn-sphotos-d-a.akamaihd....x720/1460259_737265006300874_1633651861_n.jpg