Last year we allowed our new clean up bull GTWY Milestone, which is an Ali x Harrietta and a flushmate to Breathe Easy, Discovery, and Pride and Glory, breed several of our older Sun Seeker daughters. They should calf at the end of this month and early next month. Last year we bred our yearling Sun Seeker heifers to Grizz and SS Goldmine L142. We were pleased with the Grizz calves we had out of heifers in 2009, so we elected to use him again. Our hope was to obtain calving ease, while maintaining some growth and consistency. I do not have any experience with Tyson or Shiver, so I cannot guide you one direction or another on those two bulls. I know many people have been pleased with the Ali calves, if you have the semen, and Northern Improvement seems like he works well phenotypically but maybe doesn't add the growth when compared to other bulls. Another bull to watch is Grizzly. I have heard many good reports on him. Hope this helps!