The MOC3041 data sheet mentions two DIL packages: One with 7.62
and one with 10.16mm spacing. The 7.62 appears the standard version,
so let's switch to that.
AC mains might be fused at 16A, while our dual-layer 3.81mm traces
don't really sustain more than 10A (assuming 35u copper). Let's
fuse by default with 6.3A which is fine for any heating up to 1.4kW.
In my use case the heating has 70W or 300W, so I could even fuse lower.
While the TRIAC is often thought as a unipolar device behaving identical
in both directions, it actually is not in terms of the gate
voltage/current. Let's fix that mistake in the v1 design.
Harald Welte