Steady Stiching - yes, you are right. The video gives the amounts for Seville oranges, so if you have a different citrus fruit the proportion of sugar to fruit has to be adjusted. Getting the set all depends on the proportions of sugar, acid and pectin and the right amount of liquid. Why not go ahead and try the clementines recipe? Make the most of the fruit while it is in season!
Murphy1 - I've been thinking and know what I would try if I had kumquats. Do you want me to PM you? Between us we might work out a decent recipe!
In the meantime, I am working on grapefruit recipes, and I promise you I will post videos on Youtube so you can have a go. Red grapefruits make a better marmalade than sweet oranges.