I think the chances of you finding internal power to any appreciable level in aikido are slim to none. Personally, I have never met anyone in Aikido with internal power /aiki. Nor have I seen a video of any teacher- Japanese or otherwise -who exhibited much.
I agree and disagree- its a ying and yang thing.
And I don't care to explain too much other than the way of these bullet points:
1. Aikido doesn't have Internal Power according to the ownership and design of and by the Chinese martial arts defining Internal Power. Yet, Aikido has its own Internal Power. O'Sensei clearly demonstrated it, as many of his deshi did as well. But, it may not be classified as such according to the Chinese's martial art's definition.
2. I have read that some people define Internal Power by their own definition of what they do which they don't associate with Internal Power as being of the Chinese martial arts.
3. Is there a standardize definition of Internal Power, the Chinese martial arts is the model. But theterm is subjective as definitions exist and vary greatly depending on whom you talk to. And who you consider on not consider an expert in Internal Power. And there are some who use Internal Power as a term interchangeable with the words or concept chi or ki.
5. If Internal Power is Physics applied say to Kinesiology then it is a matter of skill, and knowledge of creating internal power. In stead of relying on muscular development and use. Personally, I think that is what the old books by Chinese masters are referring to when it comes to internal power. They are early scientists without the scientific langauge or training to covey their findings. Physics existing in Aikido allows for Aikido's principles to be internal power.
6. If Internal Power isn't physics, and is related to another function, such as stated by some by the use of the fibrous connective tissue sheath of the body to create power as martial art technique coupled or not couple with #5. Or a force such as chi or chi gong etc. then it varies widely on the definition depending on who you are talking to. This allows for Aikido's principles to be internal power too.
I think this topic will be argued and will create many opinions regarding it. But, until there is an ultimate authority on what is or isn't internal power, because it is a subjective term, it will be a term of debate. It will be right up there with all similar debates of religion and God.