Some of the parents are mentioning their kids who are not skipped and how they are still a few years ahead of grade and some are mentioning kids who are skipped and who are also still above grade level, etc. The way I looked at it when skipping a young for grade child (who is female, though) is that we went that way when coming close to meeting her needs socially and academically was nearly impossible without the skip.
When you are dealing with a child who is a few grades ahead in many subjects, it might be possible to meet those needs with a combo of enrichment, subject acceleration, and GT programming if available. In our dd's instance, she was easily at the point where she would have been able to do well in high school honors level coursework in science and language arts (reading, writing, everything in LA) by about age 9 (4th grade). She was in that realm of being a few grades ahead in math, but not nearly as accelerated as she was in other subjects. If all of her achievement levels had been at the same level as had her math, I probably would not have agreed to skip her and would have pushed instead for subject acceleration or more GT options.
I'm sure that there are different issues for boys (I don't have one of those), though, in relation to puberty. My dd has not minded being one of the later developing girls and I understand that it generally isn't a social liability for girls (actually that being one of the first to develop can be hard for girls).
Size-wise my grade skipped dd is average or even a bit tall for her age. My younger dd, OTOH, is very short and petite build (around the 5th percentile). We did get the argument about not starting her early in K b/c she was so small but I've generally looked at it this way: if the child is small b/c s/he is way younger and not b/c s/he is going to be smaller than age-mates for his/her whole life, that is one thing. If the child, like my dd, is likely to be short forever (we have many 5' tall women in both my family and dh's), I would not hold him/her back academically in the hopes of making the size difference lesser. A small person will need to learn to deal with the fact that s/he is just smaller than others. Dh is 5'6". As an adult, he has to deal with the fact that most men are a lot taller than he.
I guess that what I am getting at is that I would not use size or later puberty as the deciding factor against a skip if all other indicators point toward it not just being an option but being necessary in order for the child not to suffer academically. It is something to consider, but only one piece of the puzzle.
