Want more projection in upper poles - Would using filler affect fat retention?

Hello I had an augmentation with fat transfer 3 months ago. I’m very happy with the results and retention and don’t want more volume. I’d like however more projection in the upper poles, cleavage area. I’m very skinny and absolutely cannot undergo another round of lipo (i hated the post op of lipo and can’t do it again). I’m considering doing a minor top up in cleavage with fillers. Would it affect fat retention? Could I do it now? Are there any major concerns, other than it being temporary?