Is your starter button still divorced from the ignition circuit on the key?
I am running significant initial advance - which can lead to (and my case does result in) hard starting when hot. It is as if the initial firing cylinders are pushing back against the starter motor when cranking with the coil on.
To prevent this I hold the starter button down until the engine is spinning as fast as the starter will turn it - and THEN engage the ignition circuit with the key. Works like a charm.
