Since the average IQ is in decline as a result of dysgenic fertility, what if there is a trade-off between decreased IQ and disease resistance? In terms of unforeseen genetic trade-offs, is it any better if our average IQ is artificially decreasing (dysgenics) or artificially increasing (eugenics)? (And for evidence that it is decreasing, see Dysgenics by R. Lynn).
Also, there is plenty of indirect evidence that the number of genes which govern intelligence is relatively small. Selecting for IQ would have no real effect on genetic variation, and any pleitropic side-effects would be minimal; for instance,
The results of these studies also imply that the genetic variation in intelligence depends on a relatively small number of genes because the possible variability between even closely related individuals seems to be enormous
I see that you are avoiding answering my question whether you actaully have any experience from breeding for traits...