[Freesurfer] PETSURFER - smooth question

Dear FS experts,

I've been working with the proposed pipeline, but I still have a doubt regarding the degree of smooth to be applied to the final surfaces prior to the analyses.

The first question is that, given a "standard" PET scanner, with a PSF between 5-8mm, what size smooth would you apply? Would 10mm or 15mm be reasonable (as for MRI)?

The second question is if it is correct, in your opinion, to use the same size of smooth kernel for a multimodal PET and MRI analysis (i.e., local intermodality correlations, for example FDG and MRI)? Or, given the more smooth nature of the PET signal, would you apply a lower degree of smooth to the final PET surface?

Thanks in advance for your advices, Edu V.