With the information we got today on mumble it seem that the minimum fee for transcations would be around 1 cent.
So it would make sense to use around 2-3 bts as the cheapest fee (around 1 cent but slightly below to have a nice selling agrument).
(Here comes the limit of my hability to express myslef clearly in english ...)
To avoid to hurt referral program, wich is a very sensible subject, we could have something like 150-300 bts as the upward cap fee.
The low cap is easy to decide, it's the minimum fee that doesn't allow anyone to hurt the ecosystem. The top cap is more tricky !!!
To define the top cap, maybe we could create a poll and get an estimation of how much transactions (in volume) we would have with fees of 3 bts / 30 bts / 100 and the maximum fee (let's say 300)
With something like 20 members participating in the evaluation we would have something close to what we would have. With simple math we could determine what would be the highest fee asked to keep (more or less) the same effect on the referral program and probably decide to take something a little higher to be sure.
This would be to avoid guessing in the dark and change it in 5 weeks with all the fudders enjoying the oportunity to say that "we are always changing everything and bla bla bla fud fud fud"
Is that making sense ?