Not sure whether FP use a tape or a 2 part rubber putty but it is a soft flexible material when cured. What the dealer suggested is basically what I have done on both my FPs. I have actually removed and rebedded my front windows on tha Maldives
and that was a nightmare. Your small side windows less so. When the new seal started to bleed black I used 1 part polyurathane sealant and made a fillet round the edge using a round former. The dealer is right, you need to mask otherwise cleaning
off the extra is a real pain.
On the Athena I had serious black bleed on the saloon
window. The sealant adhesive was already undercut by years of washing
to remove the bleed so I filled the gap and added a fillet. The front windows are next.
While the absolutely correct thing to do is to remove and rebed the windows, yours are small and not structural, I would just do as I originally suggested. Undercut the rubber with a narrow chisel, clean as well as possible, mask up, get primer in the gap maybe using cotton buds, then gun in the Sikaflex and fair the edge, remove tape and spray with water
to cure polyurathane.
Just be careful when craning Lavezzi, you need a travel lift
or spreader bars the same width as the boat, otherwise the flexing can pop the windows.