Surface Shaders : Change blending options for base/add passes?

Is it possible to change the blending options for forward base and additive passes in a surface shader? Seems to be an all or nothing deal.

I could render two surface shaders and change each of their properties, but while there’s a directive for noforwardadd, there doesn’t appear to be one for noforwardbase.

Any thoughts?

Ideally not dropping back to writing a full multi-pass shader as that’s what I’ve just converted over to be a surface shader (trying to keep things as simple as possible as my shaders are growing slightly unwieldy and it’s easier if I can keep things to a minimum).

Ignore this post. Thought I’d fixed it but the issue still stands.