Poketransfer

I'm having some problems importing pokemon I made with pokegen from my pearl version to my black version. It keeps saying that it can't read my save data. Is there some type of hack shield or do I have to get so far into the game before I can use poke transfer(I just started my pearl version). Can anyone help me make better pokemon that will be able to pass this hack shield/tell me how far I have to get in pearl, I really put a lot of effort into making them look legit(I read the guide and the only thing I could have done better was made the IVs random) and I would really like to be able to use them if at all possible on my black version, but I don't really want to use my action replay on a version I put effort into, as it might mess something up( I really messed up my ruby version by using AR on it). I plan to get the other version that I will use AR on soon, but for now, I need my pokemon to be made in pearl and be able to transfer to black version.

Also I'm having an issue with pokegen, it only lets me set 1 nature for the entire party, and to change natures, I have to exit and reopen the program, is there some way around this? Also would really high IV pokemon be able to pass the legality checks and battle over wifi(the stats are all still within the legal limit)? I specifically made a team for battle over wifi and I would like to know if that's even possible with them, assuming someone knows what I'm doing wrong not being able to transfer them.