I have a tennis related forum. Our question is:
Write down, in the order they appear, the terms that are NOT tennis related: ace, deuce, net, racquet, bogey, serve, ball, alpine, score.
I find that it is better to have the people identify something that is not like the rest. AI still has issues with that. It has worked very well for us.
Also, you may have a low flow site (it sounds very specialized) so there is an extension that forces the registering person to post a justification for registering. It has worked well for us.
Hope you have fun with your forum