Linebacks do not affect my bids other than to be able to buy an animal cheaper than I normally would and possibly buying more animals than I would normally. However, any white higher than a high sock on the legs takes me out of a bid. Symmetry is always worth a few extra hundred to me such as a feather neck the same on each side. If feathers were symmetric, I would bump my bid up about $500 if I had to. Feathers are worth more to me than anything else other than the color red. The color of red is much more important than white on the back for me. Then I look at REA, IMF, WW, and YW, etc. Actual performance data is not important to me. It allows me to save many thousands while having similar genetics since they numbers are cooked in the books.
I should also add that I have some animals that do not fit this criteria.