When you think about somebody with large amount of muscle mass starting aikido, is there any advice you would like to give?
My experience is that muscular people are very open to the aikido principles of softness and joining. They already know how to solve problems with strength, and therefore have a genuine interest in an alternative way. Otherwise, they would not care to try aikido.
What they often do need to work extra on, though, is stretching. Muscular mass usually leads to some stiffness - particularly in the shoulders, but also in hip movement. A person with several years of bodybuilding behind him or her, would probably have much to gain by doing much stretching, to soften up the body and increase its agility.
And strength is not a bad thing
Muscular people who train aikido will learn to increase the efficiency and precision of their strength, so that they do in some sense feel much stronger than before, although they ceased with regular bodybuilding.