Hey, Siz, I have some Paul Kroll Mottled Japanese too! I picked them up at the Ohio National this year. I haven't hatched from them yet. I have some BTW in the hatcher right now, and one from an earlier hatch that thinks its a quail.
So since this is a Japanese thread, let me start the discussion with the lethal short leg gene. I know when I got my first ones from a hatchery, I had no idea that they were "long legged". They looked like short legs to me. And, next to OEGB and Sebrights, they were short legged. Then I saw some real Show Japs and found out what short legs really were. The short leg gene is lethal in a double dose. Short leg x short leg = 25% long leg, 50% short leg and 25% dead in the shell. Short leg x long leg = 50% long and 50% short. So what is short? Lets get some posters with pics of legs. I haven't got any right now, but can put some up in a day or so if we don't have any others. Sometimes the newly hatched with their big yolk bellies have such short legs that they just sort of paddle around and have trouble getting anywhere until some of the yolk is better absorbed. In addition to the lethal gene, many breeders have some problems with fertility. Many pluck or trim the feathers around the vent to make contact easier.