Re: second SIM
I don't know for sure, as I have not used a phone with more than 1 SIM slot before, but i would have thought that if you are in an area where there is no signal, it doesn't matter if you have 2, 3, 5 or more SIM's, they're not going to help.
My understanding for multiple SIM's is, 1) you spend lots of time in 2 areas, with good signal on two separate networks, 1 SIM for each. 2) you have a really good minutes plan and a really good data plan 1 SIM for each. And you switch between the two as required.
The only way that i can see that the proximity of Twonks could affect the usefulness of your 2nd SIM, is if you have chosen a 2nd network that only has coverage in areas frequented by Twonks.