I always heat sink them.. But, I've never run so much power that I've seen an AC SSR actually heat up..
I use them on my Sanyo systems running up to 10A at 240vac.. Never seen one get up to 80F..
AC SSRs aren't designed to run hot.. They are either off or on..
Anyways, I'm done with DC SSRs.. I don't have any.. Not going to buy any more.
They aren't cheap like AC SSRs.. I'm never going to use one again,
unless someone gives them to me for free..