Re: Aikikai Dan Ranks
Hi Phil Smith and Carsten are both correct.
I have friends who wished to grade under Aikikai with Tamura Sensei.
One ikkyu could not as he had not taken a shodan with his own federation,
The second, a uk based nidan was only allowed to take shodan.
The third, a uk based sandan, following discussion with Tamura Sensei whom he had known for a considerable time, was (eventually) allowed to take an Aikikai Sandan. He had to pay for shodan, nidan and sandan but does not seem to have had to wait for certificates.
I wouldn't be unduly concerned with rank freeze - your students can always grade within your own organization and if they wish to have Aikikai grades then they can take them too.
Hope this may help