(I'm going to call them 'large' and 'small' sizes, because I haven't verified the model numbers of the sets that I've used, and can't be certain I'm talking about the same thing...)
I bought a 'large' Trangia set in the late 80's and obviously it is more than adequate for two people and by adding an extra-large pot or wok that sits on the pot stands in their up-turned position, I have used it to cook for up to six people at a time.
I have found that when using the standard pots on the 'large' Trangia, It is really only just barely enough for two people if it's an all-in-one-pot meal. However, the 'large' Trangia works fine for up to four people if using both standard pots (eg, rice in one pot and curry in the other, swapping them on/off the burner as required) - which is convenient for us, because we now have two teenagers.
I have good friends (a married couple) who used their 'small' Trangia set for many years for the two of them, and they are not small eaters. So their usage indicates that it ought to be fine for two people. (They now have 4 kids and use two large Trangias!). I do not know what kind of cooking they were doing.
I reckon that if you are doing simple add-boiling-water type of meals, then the 'small' Trangia would be perfectly adequate for two people. But for more complex cooking, especially if using just one pot, I would find the 'small' Trangia to be too small for two people.
Try out a couple of your bushwalking meals in the Trangia at home, and see how it goes!
Bill P wrote:a 4 person trip which went well, except for the persistent demands of " Is that thing on?"
You probably already know this, but... A Trangia will cook very slowly if the burner contains too much metho. Don't fill it right up - it burns better when about half full. You want the flame to be coming from the small holes around the edge, not from the large hole in the middle.
(I no longer use metho at all - I've got the gas conversion on my Trangia now. Much less hassle, even if a bit finicky in sub-zero temperatures. I now only use the Trangia when cooking for more than two people. It's still the best stove I've ever used, but it is large and heavy. It's amazing how you can cook on it in a wind-storm.)