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I think you see exactly what I mean, David. At first I didn't know but then re-read your post more carefully.
By dial-in, you do understand, I am refering to a thermostat with a companion or integral modem which you access by telephone, to set up the temperature ahead of your arrival.
In lieu of over-sizing the boiler, I prefer to proportionately over-sized the radiation. And with a properly designed boiler you control temperature by the only other variable you have: Time. Bingo!