This a nice mod job! I filled in the dimple with a little copper, than used plenty of AS5, but didn't need near as much as with the dimple. Mine I have cranking at higher amps, and it does really well with the heat.
You are losing 2.8% output by using the stock copper board w/dielectric layer, vs. a Noctigon or SinkPAD -- look at 3.5A on the charts/graph here: https://budgetlightforum.com/t/-/25978. But of course this doesn't account for other side effects, like heat over running it for several minutes.