Hey everyone, I am I'm the process of building my head and I wanted to take care of the Oiling issues on my RB25 since I will have the motor taken apart...
I am putting the Tomei oil restrictor, building a 8quart oil pan and making a -12an oil drain in the back of the head.
Now my question is: is it possible what I might have too little oil in the head? since I'm already reducing the flow with a restrictor and the drainage will be severe after all the stuff im doing.

It's possible, sure, but I have never heard of it happening on an RB. The oil pump will puke it's guts up, sure, but never heard of one underoiling. The oil you are draining out of the back was not really doing anything positive by being there. It's not pressurized anymore, it's just pooling up.