It is common to have to make orthotic adjustments for a prominent fifth metatarsal base. However, it is important to note on the prescription form whether the styloid process is prominent laterally or plantarly. There is a distinct difference in accommodating for these two.
If the styloid is prominent plantarly, I recommend using a sweet spot. If it is prominent laterally, I would recommend adding extra lateral extension at the base of the fifth metatarsal. If it is prominent both laterally and plantarly, I would recommend both of those accommodations.