me too got the 6port j6413 with proxmox and opnsense with passthrough nics, works good so far.I picked up the 6 port j6413 version from topton to use as an opnsense firewall/router. I ordered on Nov 1, and received it on Nov 15th. I did take a look at the heat sink clearances. Mine looked ok. Removed the copper plate, sanded surfaces smooth replaced the thermal paste with new stuff. I have it up and running the latest opnsense with a few plugins. Sits at about 45c. virtually no cpu being used ~5% even tho I setup a few ports to be bridged ( was told this was hard on the CPU because of routing packets need to be inspected by cpu if you setup a bridge. Anyway so far pretty happy with the purchase.
--pat
What did you exactly do to check cpu cooling, sry i dont really get the steps. I would like to check mine also
BR