Pot light with vapour barrier advice

Hello,

We are installing a set of recessed lights in our first floor dining room and all is going fine except for two.

All lights so far have a bedroom above and open so there were no issues with holes and fishing the wires, all working fine.

The final two that we want to put in are located at the front of the house. The bottom floor is slightly larger then the top floor, so we have a sloping roof above for a couple of feet to the outside. Due to this there is blown insulation and a vapour barrier below it between the ceiling sheetrock.

For one, I wonder if the vapour barrier is more to hold the blown insulation in rather than actually a vapour barrier?

The recessed can lights that we have are Ic-rated and claim to be air-tight. I know that when I am installing these lights through a vapour barrier, we need to install a boot but how would this be done without any access to the small space above where the roof is sloped and insulated?

Thanks for any advice.