Sharon fruit jam?

Haven't done that one and I can't find it on my list of fruit pectin levels, however........

to get a rough idea of the pectin levels if you stew some of the sharon fruit slowly in a little water until it is pulpy, then put a teaspoon of the pulp in an old jam jar with about a centimetre of methylated spirits, wait a couple of minutes and look at the fruit pulp you put in the jar.

If it is a thick jelly like blob it is high in pectin
If it is holding together but is a slightly spread out it is medium and
if it is barely holding together it is low.

Low would not be a problem, as you could either use jam sugar with pectin,
or that pectin powder (some people like it but I find it powdery and synthetic)
or my preferred option is to add 8oz of grated Bramlet apple to each 2 lb of low pectin fruit: gives a good set without overpowering the taste of the main fruit.

Hope this helps.