For locking, it seems it would be 1:2:4. For the rewards, however, it seems it would be 1:3:6
That's the rub.
Yes, you can make it work. However, the more people in a swap group the more unstable for a couple reasons. You increase the random odds of someone dropping for quitting the game or suchlike reason by 50%. The chance for dissatisfaction goes up remarkably becaue of the third place Rewards.
It's somewhere between a little and a lot traumatic for groups to break up, especially for Arc leveling. It's most likely the longest hardest commitment a player will make to that point in the game with a lot gamewise at stake.
I'd recommend another style for more then 3 players. There's a lot (I mean a LOT!) of different 4+ player groups out there. In my main city I was in a bucnh as either Arc grower or sugar daddy.
Dig around the forum or ask for advice on one of those. While I;ve been part of a couple dozen types of leveling groups over the years, I'm no expert on any of them.
Or if you have more questions or just want to discuss reverse triangle, feel free to ask.