Idealism is more Rational than Materialism

[Rational AKD]

If we're going to make the fewest assumptions, then it would be better to say: My own consiousness is fundamental, and all other consiousnesses are mental projections

yes, which is why I addressed that by pointing out problems with solipsism.

That's just as many assumptions as: My own consiousness is fundamental, and physical substances are mental projections

not even close. first, 'my own consciousness is fundamental' is undeniably true on a perceptual level. making an unnecessary assumption involves assuming something to explain something in your experience... not assuming something is not involved in your experience. it should be evident that assumptions include what adds to the postulations... not what subtracts. consciousness assumed fundamental is subtracting the postulation of a world independent of consciousness. not adding anything unnecessary.

You are then making more assumptions with the former when you say that other consciousnesses also exist, along with some sort of network of consiousness.

the extra-consciousness is concluded due to problems of solipsism. since 'my' consciousness doesn't appear to be in control of everything in my experience, there must be something outside of it that is. but even if we regard this as an assumption, it still makes less assumptions than materialism while still explaining experience adequately. you have:
materialism assumes material objectively exists and makes up our consciousness and conscious experience, and our conscious projections are descriptions of this material world. idealism assumes extra consciousness, which would be the greater conscious, is behind our experience and consciousness. so... materialism makes 3 assumptions.
1. material objectively exists.
2. this material world is behind our consciousness.
3. our perception accurately represents this physical world.
idealism makes 1
1. a higher consciousness is behind our consciousness. that's it...

You make the mistake when you talk about your experience of your own mental processes, but don't use this as your "fundamental"

but I don't do this without reason... I've stated my reasons for rejecting solipsism many times.

This isn't what you've experienced.

but it better explains what is undeniably part of my experience... lack of control of most everything. as I said, cut out unnecessary postulations... but a source of my consciousness seems necessary to explain my lack of control of my conscious experience.