wheel - 2:26 pm on Apr 26, 2010 (gmt 0)
From a ranking benefit, #2 is clearly the best. If you do that though, have a conversation with each of them first, don't just cookie-cutter the links. Get an individualized link from each site.
I used to have a competitor to a calculator service I offered. He required a 'powered by' link from each of his clients. I didn't. Years ago he temporarily ranked for some very nice terms as a result of all those links, but no more.
In other words, treat the scaled down gadget as a tool for negotiating links, not a standardized version.
The other thought I have is, if you do tests, could you create a full practice test? That might be of more interest to your associates to publish.