In the Pomona’s Cooked Recipes – Low Sugar or Honey, it is essential to stir the pectin into an amount of sweetener in the range given in the recipe because the pectin will only dissolve in a low-sugar mixture. Any additional sweetener should be held aside until after you have added the pectin-sweetener mix to the boiling fruit and stirred vigorously for 1 to 2 minutes to get the pectin dissolved. Once the pectin is dissolved, you are free to add extra sweetener above the range. Stir in the extra sweetener well and bring the mixture back to a full boil before turning off the heat.
Be aware that adding extra liquid sweetener can soften the jell, so consider adding a little extra pectin in Step 4 if you will be adding extra liquid sweetener.