The hard part is that you are embarrassing your Sensei and school...even more so than yourself. They were the ones that put you up to test after all, and the school that sent a poor quality Aikidoka up will be judged by the quality of student they present to the technical comity.
I've heard to many stories about Yamada Sensei, or other Technical comity members "having a word" with the Sensei of failing students. I've heard of Yamada Sensei "having a word" with students who had passed, but barely passed, black belt tests as well. So my only opinion would be is, if you are going to test, be prepared. I think you are gonna want to look like a black belt on the test coming off the bat. It is embarrassing to pass, but pass while struggling.
Agreed... (I've seen other shihan "have a word" with various sensei also. Most of the sensei I've been around have wanted people going for their tests to be so good with the test in question that they were almost ready for the next level... (e.g., a person going for 1kyu being completely familiar with shodan requirements).