Really beautiful! I felt in love with eva stamps when I tried them a couple of months ago.
This is a perfect example on how it is a wonderful resource. Here you can make a quick and cheap tool to get an amazing result, as you can make a bunch of them, for different colours and shapes.
I have some stamp inks pending on my wishlist, as I used regular stamp ink back then.
Please let me recover that project here to compare settings, as I remember I only used one or two passes
DIY Project Sharing | Craft Foam Hearts Stamps
EDIT:
But this is for the Crafter, it would be around 13,2 force in the iCraft, if that makes sense (remember my conversion table is only a theory)