Ah, much nicer. I misunderstood your post on HSM.
You might sneak some holes in on the sides or something. Otherwise I can't see any path for airflow at all in those pictures.
The safe thing is to measure it. Our old rule-of-thumb was that a 1in^2 surface, vertical in free air, would rise to 60C with natural convection, or ~35-40C/W over ambient per in^2. I don't know how accurate it was, but that was the Old Man's ROT.
This random sample from Aavid has 1.7in^2 of surface area, and they rate it at 24C/W. I take that as their natural convection rating, which works out to 41C/W/in^2).
That assumes free air, which you may not have if there's no ventilation.
In your favor is that you don't have to dissipate the whole 9W. LEDs are so efficient these days that they radiate several watts as light.
Ha! :-) (I thought of that for mine too, before I made the 'beer can' heat sinks :-))
Cheers, James Arthur