The tins of gel fuel as bought are too big. I'm waiting to run out of shoe polish so that I can use the tin instead of forking out £7 for the Trangia tin
However in the interest of science I have had a wee play. Here are my findings.
I made a cup out of tinfoil to fit in the pot holder, decanted some gel fuel into it and put a cup of water on to boil.
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However, the water did not boil at this distance.
So I made another cup to fit the upper tier
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And Bingo! We had boiling water.
So from this terribly unscientific test, I would say that it would be difficult to get water boiling in a sensible time from the base of the pot holder because of the distance, so I think there might be a similar problem with the Trangia Gel tin. I have found that the optimum distance of about 2 inches between the gel and pot.