Hi Paul, per my experience if you force dormancy on plumerias, the inflo will not bloom (the buds will slowly drop off) but you will have additional tips next spring.
Some people are successful in letting their inflo bloom through winter time by keeping the plummies with inflo indoor on Southfacing window, where it can receive sufficient light that will make the buds open up/bloom. I was only successful on my Dwarf Pink Singapore but the other plants, with or without inflo gets dormant winter time because I leave them outside.
Here's wishing you would find a way for that first time bloomer to bloom first time of the year.
