I definitely wouldn't do it at 5 months. I prefer to wait until at LEAST 8 months. Jackson was 7 1/2 months, and is fine, he was already pretty much full grown at that point, but if I got a boy in the future, I'd wait a bit longer for those growth plates to close.
IMO, if you are a VERY responsible owner, there is nothing wrong with not neutering your dog. For my own sake, I prefer a neutered male, but as far as health risks vs. benefits, I really feel they are equal on both sides (as far as males go).
Here is some great reads, pretty unbiased:
http://www.naiaonline.org/pdfs/LongT...uterInDogs.pdf An Error Occurred Setting Your User Cookie